Tryptophan aminotransferase activity in rat liver

Area of Science:

• Biochemistry
• Enzymology
• Metabolic pathways

Background:

• Tryptophan aminotransferase activity in rat liver is not fully characterized.
• The role of tyrosine aminotransferase in tryptophan metabolism requires elucidation.

Purpose of the Study:

• To quantify the contribution of tyrosine aminotransferase to total tryptophan aminotransferase activity in rat liver.
• To investigate the mechanisms underlying the induction of tryptophan aminotransferase activity.

Main Methods:

• Utilized an antiserum against rat liver tyrosine aminotransferase.
• Measured enzyme activity in rat liver extracts under various conditions (e.g., tryptophan or triamcinolone administration, starvation).

Main Results:

• Rat liver tyrosine aminotransferase catalyzes approximately 60% of tryptophan aminotransferase activity.
• Induction of tryptophan aminotransferase activity by tryptophan or triamcinolone is solely due to increased tyrosine aminotransferase activity.
• The remaining 40% of tryptophan aminotransferase activity, which increases after starvation, is of unknown origin.

Conclusions:

• Tyrosine aminotransferase is the primary enzyme responsible for tryptophan transamination in rat liver.
• The role of tryptophan transamination in overall tryptophan metabolism appears limited.
• Further research is needed to identify the enzyme(s) responsible for the remaining tryptophan aminotransferase activity.