ENZYMIC CONVERSION OF 3-HYDROXYANTHRANILIC ACID INTO CINNABARINIC ACID BY THE NUCLEAR FRACTION OF RAT LIVER

Area of Science:

• Biochemistry
• Enzymology
• Molecular Biology

Background:

• The metabolism of 3-hydroxyanthranilic acid is linked to various biological processes.
• Understanding the enzymes involved is crucial for elucidating metabolic pathways.

Purpose of the Study:

• To identify and characterize an enzyme responsible for converting 3-hydroxyanthranilic acid.
• To determine the properties and optimal conditions for this enzymatic reaction.

Main Methods:

• Isolation and purification of a nuclear enzyme from rat liver.
• Enzymatic assay to study substrate conversion.
• Spectroscopic and chromatographic analysis for product identification.
• Investigation of enzyme kinetics and cofactor dependencies.

Main Results:

• An enzyme was identified in the nuclear fraction of rat liver catalyzing the conversion of 3-hydroxyanthranilic acid.
• The red product was isolated, crystallized, and identified as cinnabarinic acid.
• The enzyme exhibited optimal activity at pH 7.2.
• Heavy metal ions (Ag+, Hg2+, MoO4 2-, Fe2+, Cu2+) inhibited the enzyme, while Mn2+ showed activation.
• The reaction was sensitive to sulfhydryl reagents, suggesting the involvement of disulfide groups.

Conclusions:

• A novel enzyme in rat liver nuclear fraction synthesizes cinnabarinic acid from 3-hydroxyanthranilic acid.
• The enzyme's activity is modulated by metal ions and is likely dependent on disulfide bond integrity.
• This finding contributes to understanding tryptophan metabolism and the biosynthesis of phenoxazine derivatives.