Which mineral is required for the proper functioning of the enzyme responsible for the conversion of tryptophan to niacin?

A Iron
B Zinc ✓
C Copper
D Manganese

Explanation

Zinc is a mineral that acts as a cofactor for the enzyme kynureninase, which is involved in the conversion of tryptophan to niacin.

Mnemonic

'Zinc' sounds like 'zippy', zinc helps enzymes work zippily

Source

Harper's Biochemistry
Minerals and Trace Elements Biochemistry Enzyme Cofactors Medium MEDICAL Confidence: medium