Download 49. enzyme review - Khan Usman Ghani

Journal of Medicinal Plants Research Vol. 6(6), pp. 932-933, 16 February, 2012
Available online at http://www.academicjournals.org/JMPR
DOI: 10.5897/JMPR11.494
ISSN 1996-0875 ©2012 Academic Journals
Review
Enzymes: A review
M Akram1*, Ejaz Muhiuddin2, Afzal Ahmed3, Shahab-uddin1, Khan Usmanghani4 and
Syed Muhammad Ali Shah5
1
Department of Basic Medical Sciences, Faculty of Eastern Medicine, Hamdard University Karachi, Pakistan.
Department of Surgery and Allied Sciences, Faculty of Eastern Medicine, Hamdard University Karachi, Pakistan.
3
Department of Medicine and Allied Sciences, Faculty of Eastern Medicine, Hamdard University Karachi, Pakistan.
4
Department of Pre-Clinical Sciences, Faculty of Eastern Medicine, Hamdard University Karachi, Pakistan.
5
College of Conventional Medicine, the Islamia University of Bahawalpur, Pakistan.
2
Accepted 23 December, 2011
Enzymes are made of protein that is present in all living organisms. Enzymes convert substrate into
products and are biological catalyst. These increase rate of reaction and remain unchanged by
chemical reaction. In this review article, clinical significance, regulation and inhibition of enzymes have
been elaborated.
Key words: Enzymes, function, regulation, inhibition.
INTRODUCTION
Enzymes are protein specific biological catalyst that
accelerates the rate of reaction. Enzymes act on
substrate as a result substrate is converted to product.
Substrate binds on active site of enzymes that is specific
for substrate (Hansen et al., 1990). Enzymes increases
or decreases rate of reaction by increasing or decreasing
the energy of activation (Amyes et al., 2001). Protein part
of enzymes is called apoenzyme and non protein part is
known as prosthetic group (Harris et al., 2002). The
traditional understanding is that an entirely new
complement of digestive enzymes is secreted by the
pancreas into the small intestines with each meal (Lerner
et al., 1991). This is thought to be necessary because,
like food itself, these enzymes are degraded during
digestion. In this review, we discuss experiments that
bring this point of view into question. They suggest that
digestive enzymes can be absorbed into blood,
reaccumulated by the pancreas, and reutilized, instead of
being reduced to their constituent amino acids in the
intestines. This is called an enteropancreatic circulation
of digestive enzymes (Stephen et al., 2002). Enzymes
and their sources have been given in Table 1.
The process of digestion produces glucose, amino
acids, glycerol, and fatty acids. The energy in glucose is
*Corresponding author. E-mail: [email protected].
Tel: 92-021-6440083. Fax: 92-021-6440079.
used to produce ATP via the reactions of glycolysis,
cellular respiration, and the electron transport system
(Table 2). The body uses amino acids to construct
proteins. Excess amino acids can be used to synthesize
pyruvate, acetyl CoA, and alpha ketogluterate, which
enters the Krebs cycle. Glycerol and fatty acids can be
converted to pyruvate and Acetyl CoA and then enter
cellular respiration (Kraut, 1988).
ENTEROPANCREATIC CIRCULATION OF DIGESTIVE
ENZYMES
Intact digestive enzymes can be absorbed by the
intestine and resecreted by the pancreas. The pancreas,
therefore, appears to be able to recycle proteins much as
the liver recycles bile salts, although the magnitude of
this process remains uncertain (Leibow and Rothman,
1975; Landry et al., 1993).
Diabetes mellitus and digestive enzymes
Diabetes mellitus is a metabolic disorder due to relative
and absolute deficiency of insulin resulting in
hyperglycemia and glycosuria. Researchers are
searching new drugs that modulate blood glucose
concentration through inhibition of the enzymatic
breakdown of complex carbohydrates to meal derived
Akram et al.
933
Table 1. Enzymes and their sources.
Enzyme
Chymotrypsin
Trypsin
Papain
Bromelain
Source
It is a proteolytic enzyme crystallized from an extract of the pancreas gland of the ox.
It is a proteolytic enzyme also crystallized from an extract of the pancreas gland of the ox.
It is derived from the green papaya fruit.
It is extracted from the pineapple. Because of the relative value of the fruit.
Table 2. Clinical significance of enzymes.
Enzymes
Aspartate aminotransferase
Alanin amino transferase
Amylase
Lactate dehydrogenase
Acid phosphatase
Alkaline phosphatase
Lipase
Glutathione reductase
Isocitrate dehydrogenase
glucose absorption. Acarbose is prescribed in diabetes
mellitus mellitus. It inhibits α-glucosidase and as a result
disaccharides and polysaccharides cannot break in
glucose. Many herbal extracts have been found to
posses similar inhibitory effects. Some herbal drugs have
similar activity and are proved effective in treatment of
diabetes mellitus. Ginger (Zingiber officinale Roscoe) has
developed a reputation in treatment of several diseases.
In vitro enzymic inhibitory effect of Z. officinale was
evaluated in a study. In this study, Z. officinale extract
and Acarbose was investigated for their efficacy to inhibit
enzymes α -amylase and α glucosidase. These two were
allowed to react with cooked rice and percentages of
glucose content were measured. The glucosidase and
amylase activities on the rice were inhibited by addition of
ginger cause significant reduction in glucose percentages
which showed comparable results with Acarbose on
glucosidase activity. This study indicates ginger can be
used as an amylase and glucosidase inhibitor in
carbohydrate digestion (Abeysekara et al., 2007).
Withania somnifera: A novel source of asparaginase.
In one study, various plants were screened for L asparaginase enzyme. W. somnifera was identified as
potential source of the enzyme on the basis of high
specific activity of the enzyme. The enzyme was purified
and characterized from W. somnifera, a popular
medicinal plant in Unani system of medicine. It was the
first report for L-asparaginase from W. somnifera.
Asparaginase is commonly used for treatment of acute
lymphocytic leukemia and mast cell tumor, therefore, W.
somnifera can be a potential plant based therapy for
these disorders (Vishal et al., 2009).
Clinical interpretation
Myocardial infacrtion
Viral hepatitis
Pancreatitis
Myocardial infarction
Metastatic carcinoma
Obstructive liver disease
Pancreatitis
Hepatitis
Liver disorders
CONCLUSION
Enzymes are biological catalyst. They are utilized for
digestive purposes as well as in cellular functions. They
are also important in diagnosis of disease because in
some diseases enzymes, concentration increases that is,
indicative of specific disease.
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