COENZYMES

A i.e. Pantothenic acid

D i.e. Acetylation

Pantothenic acid is necessary for synthesis of coenzyme A (CoA)Q, which functions as a coenzyme for acetylation reactionsQ

[Ref Harper 30^th/e p. 62 & 29¹ p. 59]

• Coenzymes act either a donar or an acceptor of group.
  • They serve as recyclable shuttles – or group transfer agents – that transport many substrates from their point of generation to their point of utilization.

Biotin/ Vitamin H/ Coenzyme R

• It is a water-soluble B-vitamin (vitamin B7).
• It is composed of a ureido (tetrahydroimidizalone) ring fused with a tetrahydrothiophene ring.
• A valeric acid substituent is attached to one of the carbon atoms of the tetrahydrothiophene ring.
• Biotin is a coenzyme for carboxylase enzymes, involved in the synthesis of fatty acids, isoleucine, and valine, and in gluconeogenesis.

Ans. ‘D’ Pantothenic acid

CoA biosynthesis requires cysteine, pantothenate (vitamin B₅), and adenosine triphosphate (ATP).

it is naturally synthesized from pantothenate (vitamin B5), which is found in food such as meat, vegetables, cereal grains, legumes, eggs, and milk.

Pantothenate (vitamin B₅) is phosphorylated to 4′-phosphopantothenate by the enzyme pantothenate kinase (PanK; CoaA; CoaX). This is the committed step in CoA biosynthesis and requires ATP.

Ans. ‘C’ B6

Pyridoxal phosphate (PLP), a derivative of vitamin B6, is present at the catalytic site of all aminotransferases and plays a key role in catalysis.

During transamination, Pyridoxal phosphate serves as a “carrier” of amino groups.

Ans. ‘A’ Thiamine pyrophosphate

NAD+ is derived from nicotinic acid, a member of the vitamin B complex, used in the synthesis of GABA.

During transamination reaction glutamate is formed. Pyridoxal Phosphate acts as a coenzyme.