Enzyme Stimulation

Enzymes frequently require coenzymes for optimum activity. The coenzymes are usually vitamins and cofactors, invariably—electrolytes such as mono- and divalent metallic ions (e.g., K+, Na+, Ca+2, Mg+2, Zn+2, and Fe+2). These coenzymes activate different enzymes by various means of complexation and stereochemical interactions. A detailed consideration of the mechanisms involved is not within the scope of this discussion. It can be stated, however, that such ions may affect enzymes in one of two ways. Either direct interaction induces changes in the conformation or a charge on the enzyme, or interaction of the cation with an enzyme-inhibiting substance, prevents or minimizes the deactivation.

Enzymes and other polypeptide chains in biosystems have an ample supply of metal-binding groups. These are imidazole rings (in histidine), -SH groups (of cysteine), and

Table 2-1. Enzymes Inhibited by Therapeutic Agents

Enzyme

Drug

Clinical utility

Acetylcholinesterase

Neostigmine,6 echothiophate"

Myasthenia gravis, glaucoma

Alanine racemase'

D-cycloserine"

Antibacterial

Aldehyde dehydrogenase

Disulfiram''

Alcoholism

Aldose reductase

Sorbinol

Diabetes

Angiotensin converting enzyme

Captopril''

Hypertension

Carbonic anhydrase

Acetazolamide''

Diuretic

Dihydrofolate reductasec

Trimethoprim'' Pyrimethamine,''

Antibacterial, antimalarial,

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  • Kisanet
    What is enzyme stimulation?
    3 years ago

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