Download a new equation for calculating the number of atp molecules

WORLD JOURNAL OF PHARMACY AND PHARMACEUTICAL SCIENCES
Rafik et al.
World Journal of Pharmacy and Pharmaceutical Sciences
SJIF Impact Factor 5.210
Volume 4, Issue 07, 175-185.
Research Article
ISSN 2278 – 4357
A NEW EQUATION FOR CALCULATING THE NUMBER OF ATP
MOLECULES GENERATED FROM FATTY ACIDS
Yahya khawaja1, Laura Scrano2, Sabino A. Bufo3 and Rafik Karaman*1,3
1
Pharmaceutical Sciences Department, Faculty of Pharmacy, Al-Quds University, Jerusalem,
Palestine.
2
Department of European Cultures (DICEM), University of Basilicata, Via Dell’Ateneo
Lucano 10,Potenza 85100, Italy.
3
Department of Sciences, University of Basilicata, Viadell’Ateneo Lucano 10, 85100,
Potenza, Italy.
Article Received on
28 April 2015,
Revised on 23 May 2015,
Accepted on 15 June 2015
ABSTRACT
ATP, Adenosine triphosphate, is a complex entity requires for all
organisms regardless of their size. All organisms such as bacteria and
humans utilize ATP as a main source of their energy and a steady
supply of ATP is so critical such that in poisoning cases such as
*Correspondence for
cyanide poisoning the cells die as a result of protein production’s
Author
shutdown due to cyanide binding to the copper atom in cytochrome
Dr. Rafik Karaman
oxidase of the oxidative phosphorylation electron transport. This paper
Pharmaceutical Sciences
Department, Faculty of
documents a novel approach for calculating the number of ATP
Pharmacy, Al-Quds
molecules generated from oxidation of long chain saturated and
University, Jerusalem,
unsaturated fatty acids with either even or odd numbers of carbon
Palestine.
atoms. Our new approach is summarized in an equation based on the
oxidation states of the different carbons of the fatty acids. Using this
approach, the time required to calculate the number of ATP molecules generated from the
oxidation of any long fatty acid is less than 2-3 minutes whereas in the regular, current, used
approach the time needed is exceeding few hours. Furthermore, using the regular approach
dictates the illustration of all fatty acid biochemical oxidation processes while our new
approach documented herein does not.
KEYWORDS: Saturated fatty acids, unsaturated fatty acids, β-oxidation, ATP, adenosine
triphosphate, Energy currency.
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INTRODUCTION
ATP (nucleoside triphosphate) is a complex molecule consists of a nucleotide bound to
phosphate groups and is utilized as a coenzyme by bacteria and humans cells.[1] In 1929, Karl
Lohmann discovered ATP and in 1948 Alexander Todd was the first to synthesize this
ubiquitous molecule.[2-3]
Energy is generally released from ATP molecules to do chemical, osmotic or mechanical
work in the cell by a hydrolysis process by which ATP is hydrolyzed to ADP
(adenosine diphosphate) and inorganic phosphate. Then the resulting ADP is immediately
recycled in the mitochondria where it is recharged and becomes again as ATP.
ATP is not significantly unstable; however in the absence of a catalyst its hydrolysis is very
slow to insure its stored energy. On the other hand, this stored energy in ATP is readily
released in the presence of the appropriate enzyme.
ATP functions in a cyclic manner as a carrier of chemical energy from the catabolic reactions
of metabolism to various cellular processes that require energy. It is utilized in a variety of
functions including (i) transport work (osmotic work) in which different organic and
inorganic substances are moved across cell membranes, (ii) mechanical work in which the
energy is spent on muscle contraction such as in the cases of the heart, blood vessels, skeletal
muscles and etc.
This kind of work also applies on the work done by chromosomes and flagella to carry out
their many different functions and (iii) chemical work in which the energy stored in ATP
molecules is utilized to synthesize several thousands of macromolecules that the cell needs
for its survival.[4-11]
ATP biosynthesis relies on utilizing the substances found in food as sugars, carbohydrates,
fats and etc. The production of ATP by a non-photosynthetic aerobic eukaryote occurs in the
mitochondria of cell by three major pathways: (1) glycolysis, (2) citric acid cycle/oxidative
phosphorylation and (3) beta-oxidation.[4-11]
Fatty acids generally found in the form of triglycerides (in condensed and anhydrous shape)
in humans are considered a very important source of ATP supply. 1 gram of fatty acids
provides an approximately 9 kcal compared to only 4 kcal by carbohydrates. Due to the
physicochemical properties of fatty acids which consist of a large lipophilic moiety, these
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compounds can be stored in a relatively anhydrous environment and in a reduced size,
whereas, carbohydrates are more highly hydrated, therefore their volume capacity is much
higher.
Fatty acids contained in a variety of foods and are usually stored as triglycerides, which
cannot be absorbed by the gastrointestinal tract.[12-18] Therefore, triglycerides are degraded
into free fatty acids and mono-glycerides by the enzyme pancreatic lipase, found as a 1:1
complex with colipase protein. This protein is crucial for the activity of the enzyme
pancreatic lipase. For an optimal activity of the complex, fatty acids should be in a water-fat
environment. This is achieved by emulsifying the fatty acids by bile salts.
The products of triglycerides, free fatty acids and mono-glycerides, are absorbed through the
intestinal wall along with a small fraction of free glycerol and di-glycerides. Once passed the
intestinal wall, these substances are resynthesized into triglycerides and packaged
into chylomicrons or lipoproteins, which are freed into the lacteals, and from there into
the blood circulation. In the blood, these substances bind to the hepatocytes and adipocytes
membranes or muscle fibers, where they are either oxidized for energy supply or stored.
Fatty acids can be further degraded to acetyl-CoA by the beta-oxidation process. In each
round of beta-oxidation the length of the acyl chain is reduced by two carbon atoms and there
is a production of one NADH and one FADH2 molecules, which are utilized to generate ATP
by the oxidative phosphorylation process. Since FADH2 and NADH are characterized as
energy-rich entities, tens of ATP molecules can be produced by the beta-oxidation of a single
long fatty acid chain.[12-18]
The number of ATP molecules produced in cells from a fatty acid or a sugar is determined on
the structural features of the substance; 1 mole of the fatty acid caprylic acid generates 61
moles of ATP, and 1 mole of oleic acid generates 144 moles, whereas 1 mole of glucose
produces 36-38 moles of ATP. The current tool utilized for calculating the number of ATP
generated from any fatty acid is time-consuming. It is estimated that several hours are needed
for such calculations since many pathways and reaction steps are involved.[12-13]
In this manuscript, we report a novel approach for calculating the number of ATP molecules
generated from any saturated or unsaturated fatty acid with either even or odd numbers of
carbon atoms.
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In the following text we demonstrate all pathways and steps taken into consideration when
using the regular current method for calculating the number of ATP molecules generated
from fatty acids.
Since free fatty acids have negative charge their ability to cross membranes is limited.
Therefore, their permeability is largely dependent on specific transport protein, such as
the SLC27 family fatty acid transport protein, which facilitates their membrane
penetration. Upon reaching the cytosol, several processes should take place in order for the
fatty acids to be transferred from the cytosol to the mitochondrial matrix where the betaoxidation process takes place.[12-18]
In the mitochondrial matrix, fatty acids undergo beta-oxidation process in which two carbons
are reduced from the fatty acid chain in every cycle to form acetyl-CoA. The beta-oxidation
process involves four steps: (i) dehydrogenation of the fatty acid to trans-delta 2-enoyl CoA
catalyzed by acyl CoA dehydrogenase, where the carbon-carbon double bond is formed
between C2 and C3 and FAD molecule is reduced to FADH2 (Figure 1), (ii) hydration of
trans-delta2-enoyl CoA to L-B-hydroxyacyl CoA catalyzed by enoyl-CoA hydratase (Figure
2), (iii) dehydrogenation of L-B-hydroxyacyl CoA to B-ketoacyl CoA catalyzed by Bhydroxyacyl CoA dehydrogenase enzyme in which the enzyme utilizes NAD as an electron
acceptor (Figure 3), and (iv) thiolysis of B-ketoacyl CoA, between C2 and C3, catalyzed by
thiolase enzyme. In this reaction a molecule of coenzyme A attacks C3 and breaks the bond
to yield the first two carbons as acetyl CoA and a fatty acyl CoA with less two carbons
(Figure 4). This process proceeds until all the fatty acid carbons are converted to acetyl
CoA.[12-18]
There are different mechanisms for saturated fatty acids with an even number of carbons,
saturated fatty acids with an odd number of carbons and unsaturated fatty acids. For evennumbered saturated fatty acids: each cycle of β-oxidation, generates a two carbon unit
(acetyl-CoA), in a process of four steps. This process continues until the whole chain is
degraded to acetyl CoA groups; the final cycle of the beta-oxidation yields two acetyl CoA
groups instead of one acyl CoA and one acetyl CoA. For each cycle, the Acyl CoA group is
shortened by two carbons. As a result of this process, one molecule of each of FADH2,
NADH and acetyl CoA are formed. For odd-numbered saturated fatty acids: the fatty acid is
oxidized in the same manner as even-numbered fatty acid, however, the final products of this
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process are acetyl-CoA and propionyl-CoA. The Propionyl-CoA is then metabolized by
several steps to form succinyl-CoA.
O
FAD
R
O
FADH2
CoA
R
S
CoA
S
Acyl-CoADehydrogenase
2
trans-  - Enoyl-CoA
Acyl-CoA
Figure 1: The first step in the beta-oxidation of fatty acids.
O
OH
R
+H 2O
CoA
S
O
R
CoA
S
-H 2O
2
trans-  - Enoyl-CoA
L-3-Hydroxyacyl-CoA
Enoyl-CoAHydratase
Figure 2: The second step in the beta-oxidation of fatty acids.
O
OH
NAD+
R
NADH
O
O
+ H+
CoA
R
CoA
S
L-3-Hydroxyacyl-CoA
S
Hydroxyacyl-CoADehydrogenase
3-Ketoacyl-CoA
Figure 3: The third step in the beta-oxidation of fatty acids.
O
O
O
R
CoA
O
+ CoA-SH
S
R
S
CoA +
CoA
H3C
S
Thiolase
3-Ketoacyl-CoA
Acyl-CoA
Acetyl-CoA
Figure 4: The fourth step in the beta-oxidation of fatty acids.
which then can enter the citric acid cycle. For unsaturated fatty acids: the β-oxidation poses a
problem since the location of a cis bond can prevent the formation of a trans-Δ2 bond. This
problem is solved by the assistance of two enzymes, enoyl CoA isomerase or 2,4-dienoyl
CoA reductase.[13-21]
Calculations of ATP molecules generated from fatty acids[13-27]
The total ATP yield for every beta-oxidation cycle is 17, as NADH generates 3 ATP, FADH2
generates 2 and a full rotation of the citric acid cycle produces 12 (see Table 1).
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Table 1: The number of ATP molecules generated in beta-oxidation process of fatty
acids.
SOURCE
1 FADH2
1 NADH
1 acetyl CoA
TOTAL
ATP
x 2 ATP
x 3 ATP
x 12 ATP
TOTAL
Theoretically 2 ATP
Theoretically 3 ATP
Theoretically 12 ATP
17 ATP
Therefore, for an even-numbered saturated fatty acids (C2n); n - 1 oxidations are taking place
and the final process yields an additional acetyl CoA. In addition, two equivalents of ATP are
lost during the activation of the fatty acid. Therefore, the total ATP yield can be stated as:
(n - 1) * 17 + 12 - 2 = total ATP
For instance, the ATP yield of palmitic acid (C16, n = 8) is:
(8 - 1) * 17 + 12 - 2 = 129 ATP (see Table 2).
For stearic acid (C18), the ATP yield is:
(9 - 1) * 17 + 12 - 2 = 146 ATP
Table 2: Calculations of ATP molecules generated from the oxidation of palmitic acid
(C16).
SOURCE
7 FADH2
7 NADH
8 acetyl CoA
Activation
NET
ATP
x 2 ATP
x 3 ATP
x 12 ATP
TOTAL
= 14 ATP
= 21 ATP
= 96 ATP
= -2 ATP
= 129 ATP
In contrast to the lengthy and time-consuming approach described above for calculating the
number of ATP molecules generated from a fatty acid, which dictates the necessity to
illustrate all steps involved in the oxidation (degradation) process, the following novel
approach summarized in equations 1-2 enables the calculations of the number of ATP
molecules generated from any fatty acid within 1-2 minutes without the need to illustrate a
fatty acid breakdown stages.
For even-numbered and unsaturated fatty acids.
(4+CI) x (nCI) + (4+CLT) x nCLT + (4+CRT) x nCRT + (2.5xn) -3 = N
(1)
For odd-numbered fatty acids:
(4+CI) x (nCI) + (4+CLT) x nCLT + (4+CRT) x nCRT + (2.5xn) -3.5 = N
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Where CI, CLT and CRT are the oxidation states of the internal, left terminal and right terminal
carbons, respectively (Figure 5). n is the number of carbons. nCI, nCLT and nCRT are the
number of internal, left terminal and right terminal carbons, respectively. N is the number of
ATP molecules generated.
The ATP calculations by equations 1-2 from any fatty acid are based on the oxidation states
of the carbons of the fatty acid. For simplification, we illustrate the details for calculating the
number of ATP molecules generated from palmitic acid as a representative of an evennumbered fatty acid (Figure 5).
H O
O
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
+3
-2
-2
-2
-2
-2
-2
-2
-2
-2
-2
-2
-2
-2
-2
-3
Plamitic acid (C16:0)
Figure 5: Chemical structure of palmitic acid (C 16). The numbers in red are the
oxidation states for the carbons of palmitic acid.
The oxidation states for CI, CLT and CRT in palmitic acid are -2, +3 and -3. n =16, nCI = 14,
nCLT =1 and nCRT = 1 (Figure 5). Replacing n, CI, CLT, CRT, nCI, nCLT and nCRT with their
corresponding values in equation 1 gives.
(4+2) x14 + (4+3) x 1+ (4-3) x1 +2.5x16 -3 = 129 ATP molecules.
The number of ATP molecules generated from unsaturated fatty acid can be calculated using
equation 1. For example, the number of ATP molecules provided by the oxidation of
myristoleic acid is: (4+2) x10 + (4+3) x 1+ (4-3) x1 + (4+1) x2 +2.5x14 -3 = 110.
On the other hand, the number of ATP molecules generated from an odd-numbered fatty acid
can be calculated using equation 2. For example, the number of ATP molecules provided by
the oxidation of margaric acid is: (4+2) x15 + (4+3) x 1+ (4-3) x1 +2.5x17 -3.5 = 137
molecules.
Using equations 1-2, we have calculated the number of ATP molecules generated from
different long chain saturated and unsaturated fatty acids with either even or odd numbers of
carbon atoms and the results are illustrated in Table 3.
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Table 3: Experimental and calculated ATP molecules generated from different fatty
acids. aThe calculated values were obtained using equations 1-2.
Type of
Fatty Acid
Fatty Acid
Name
Margaric acid
Odd
saturated
fatty acid[23- Pentadecylic
24]
acid
Even
saturated
Caprylic acid
fatty acid[13-
Chemical Structure
ATP ATP
Exp. Calc.
Value Valuea
CH3(CH2)15COOH
137
137
CH3(CH2)13COOH
120
120
61
61
CH3(CH2)6COOH
Calculations Details
By Equations 1-2
(4+2) x15 + (4+3) x 1+ (4-3)
x1 +2.5x17 -3.5 = 137
(4+2) x13 + (4+3) x 1+ (4-3)
x1 +2.5x15 -3.5 = 120
(4+2) x 6 + (4+3) x 1+ (4-3)
x1 +2.5x 8 -3 = 61
22]
Capric acid
CH3(CH2)8COOH
78
78
Lauric acid
CH3(CH2)10COOH
95
95
Myristic acid
CH3(CH2)12COOH
112
112
CH3(CH2)14COOH
129
129
CH3(CH2)16COOH
146
146
CH3(CH2)18COOH
163
163
CH3(CH2)20COOH
180
180
CH3(CH2)22COOH
197
197
CH3(CH2)24COOH
214
214
CH3(CH2)3CH=CH(CH2)7CO
OH
110
110
CH3(CH2)5CH=CH(CH2)7CO
OH
127
127
Sapienic acid
CH3(CH2)8CH=CH(CH2)4CO
OH
127
127
Oleic acid
CH3(CH2)7CH=CH(CH2)7CO
OH
144
144
CH3(CH2)7CH=CH(CH2)7CO
OH
144
144
Palmitic acid
Stearic acid
Arachidic acid
Behinic acid
Lignoceric acid
Cerotic acid
Unsaturated
Myristoleic
fatty acid [26acid
27]
Palmitoleic
acid
Elaidic acid
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(4+2) x 8 + (4+3) x 1+ (4-3)
x1 +2.5x10 -3 = 78
(4+2) x10 + (4+3) x 1+ (4-3)
x1 +2.5x12 -3 = 95
(4+2) x12 + (4+3) x 1+ (4-3)
x1 +2.5x14 -3 = 112
(4+2) x14 + (4+3) x 1+ (4-3)
x1 +2.5x16 -3 = 129
(4+2) x16 + (4+3) x 1+ (4-3)
x1 +2.5x18 -3 = 146
(4+2) x18 + (4+3) x 1+ (4-3)
x1 +2.5x20 -3 = 163
(4+2) x20 + (4+3) x 1+ (4-3)
x1 +2.5x22 -3 = 180
(4+2) x22 + (4+3) x 1+ (4-3)
x1 +2.5x24 -3 = 197
(4+2) x24 + (4+3) x 1+ (4-3)
x1 +2.5x26 -3 = 214
(4+2) x10 + (4+3) x 1+ (4-3)
x1 + (4+1) x2 +2.5x14 -3 =
110
(4+2) x12 + (4+3) x 1+ (4-3)
x1 + (4+1) x2 +2.5x16 -3 =
127
(4+2) x12 + (4+3) x 1+ (4-3)
x1 + (4+1) x2 +2.5x16 -3 =
127
(4+2) x14+ (4+3) x 1+ (4-3)
x1 + (4+1) x2 +2.5x18 -3 =
144
(4+2) x14+ (4+3) x 1+ (4-3)
x1 + (4+1) x2 +2.5x18 -3 =
144
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The results in Table 3 demonstrate overlapping between the calculated and experimental
values of ATP generated from fatty acids. Hence, the use of equations 1-2 for calculating the
oxidation of any fatty acid is fruitful, easy and fast.
SUMMARY AND CONCLUSION
Fatty acids are a sub-class of the lipid macronutrient class. One of the fatty acids major roles
is energy production by supplying ATP (adenosine triphosphate). Fatty acids class is
considered the highest energy carrier compared to other macronutrient classes such as
proteins and carbohydrates. Fatty acids generate the most ATP on an energy per gram basis
by the β-oxidation pathway. Energy is generally released from the ATP molecule to do
chemical, osmotic or mechanical work in the cell by a hydrolysis process in which ATP is
hydrolyzed to ADP (adenosine diphosphate) and inorganic phosphate. Then the resulting
ADP is immediately recycled in the mitochondria where it is recharged and becomes again as
ATP.
The regular approach used today for calculating the number of ATP molecules generated
from an intake of a fatty acid (β-oxidation) is complex and time-consuming process that
dictates an illustration of all pathways and steps involved in the fatty acid catabolism (βoxidation). On the other hand, the novel approach reported herein and summarized in
equations 1-2 is very simple and requires a very short time (less than 3 minutes) which can
provide an easy tool to be utilized by students and researchers alike.
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