University:
Liberty University
Course:
BIOM 500 | Introduction to Biomedical Sciences
Academic year:

2024
Views:

200

Pages:

5
Author:

Sheha A.

Enzymes These are defined as "biocatalysts" synthesized by the living tissues, proteins in nature, thermolabile in nature, specific in action. *Increase the rate of reactions without affecting the equilibrium of the reaction. *Almost all enzymes in the process of metabolism are proteins in nature. Simple & Conjugated Enzymes *Enzymes with only one type of molecule are called simple enzymes. *Enzymes consisting of protein part (apoenzyme) and non-protein part (prosthetic group) are called conjugated enzymes. Protein part of the conjugated enzyme is called apoenzyme. Non-protein part of the conjugate enzyme is called prosthetic group. Isoenzymes *Different forms of the same enzyme catalyzing the same reaction are called isoenzymes or isozymes. *These are slight variations in the primary structure of the enzyme protein. *These differences arise due to variation in the amino acid sequence. Isoenzymes Isoenzymes are different molecular forms of the same enzyme that catalyze the same reaction. These enzymes have different heat stabilities, tissue localization, and kinetics. These are useful in the diagnosis of diseases. Examples: Isoenzyme form of glucokinase that is less sensitive to glucose inhibition. Hexokinase and glucokinase are the two isoenzymes which have different localizations. Different Localizations Hexokinase is present in other body cells and glucokinase is present in liver cells. They also have different kinetics. Km values are high for glucokinase and low for hexokinase. This means hexokinase is active at low glucose concentration and glucokinase is active at high glucose concentration. Lactate dehydrogenase has 5 isoenzymes: LDH-1, LDH-2, LDH-3, LDH-4, LDH-5 Creatine kinase/creatine phosphokinase has 3 isoenzymes: CK-MM (CPK-1), CK-MB (CPK-2), CK-BB (CPK-3) *LDH-1 and CK-MB is less important to diagnosis of myocardial infraction.