Enzymes are present in organisms as single units or in multienzyme complexes. Posttranslational modifications of amino acid residues take place after peptide assembly on the ribosome; hydroxylation, phosphorylation, sulfation, N-terminal acetylation, and glycosylation are a few examples. The nature of posttranslational modifications and the hydrophobicity of amino acid side chains determine whether the enzyme is free or membrane-bound.1, 2
Enzymes catalyze biochemical reactions in living systems which would otherwise proceed too slowly at physiological temperature and pH to sustain life. Specificity and high catalytic power are two special attributes of enzymes which distinguish them from ordinary chemical catalysts.3
Clinical and pharmaceutical importance of enzymes
A variety of diseases can be detected through altered body fluid levels of specific enzymes.
Table 1 Disease detection via enzymes
Aspartate aminotransferase Liver disease
Alanine aminotransferase Liver disease
Acid phosphatase Prostate carcinoma
Alkaline phosphatase Bone disease, Hepatobiliary disease
Creatine kinase Myocardial infarction, Muscle disease
Lactate dehydrogenase Myocardial infarction, Liver disease
Cholinesterase Organophosphate poisoning
Pancreas enzymes Pancreatic diseases.
glutamyltranspeptidase Liver disease, Alcoholism
Elevated plasma and urine lysozyme levels are typical for lymphocytic leukemia’s and degenerative kidney diseases with glomerular and proximal tubular damage. Normalization of lysozyme plasma levels and disappearance of lysozyme in the urine are of prognostic value in successful kidney transplants.
Various types of cancer are associated with a general increase in plasma proteinases. The presence of various plasminogen activators and their inhibitors in many malignancies suggests that the fibrinolytic system is involved in the regulation of tumor growth and metastatis. Local 日本保健食品 changes in fibrinolytic activity such as reduced tPA and increased urokinase levels in biopsies of the intestinal mucosa are characteristic in inflammatory and (pre)malignant processes in the colon.4
Replacement therapy in enzyme dysfunction or as adjusting agents in biochemical processes that have gone awry. Examples include, Fibrinolytic enzymes in thrombotic disorders; Proteolytic enzymes in wound healing; Amino acid degrading enzymes and Dimeric ribonuclease in cancer therapy; Digestive enzymes; Hyaluronidase and superoxide dismutase in inflammations, and many others.
Enzymes of nonhuman origin sometimes are potent immunogens or allergens. Their delivery systems must protect them from inactivation before the target side is reached, and yet allow the enzymes to be released at the target site, eventually with their specific cofactors if required. Nonetheless enzymes are attractive drugs because of their specificity and efficiency.5
Natural and synthetic enzyme inhibitors have become increasingly important in medicine, and have developed into a separate class of drugs. These inhibitors form tight noncovalent or irreversible covalent complexes with their target enzymes.6,7
Thrombin is a key enzyme in clot formation, acting as a catalyst of conversion of fibrinogen to fibrin. Hirudin, a potent thrombin inhibitor from leech extracts, is available as a recombinant polypeptide and is currently under investigation in various clinical trials.8,9
The bovine basic pancreatic proteinase inhibitor aprotinin inactivates kallikrein and is used successfully in supplementary treatment of acute pancreatitis and shock.10Rennin inhibitors such as pepstain are currently under investigation to lower blood pressure.11,12