Studies on the L-Amino Acid Oxidase of Neurospora crassa

Citation

Thayer, Philip Standish (1952) Studies on the L-Amino Acid Oxidase of Neurospora crassa. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/JJN0-XC39. https://resolver.caltech.edu/CaltechTHESIS:10052017-132646189

Abstract

The L-amino acid oxidase of Neurospora is a gen­eral amino acid oxidase attacking a wide range of L-amino acids at different rates. Activity of the enzyme is de­pendent on substrate concentration, oxygen tension and pH. Different amino acids show different pH optima. Activity is significantly reduced by excess substrate, and competition is exhibited between mixed substrates.

L-oxidase production by mycelium is increased 4 to 10 fold by biotin limitation. This effect is not produced by: changes in extractability of the enzyme; reduced level of growth; defective ammonia, aspartic acid, or riboflavin metabolism; or production of an inhibitor of the enzyme.

The enzyme is adaptively formed during growth in the presence of substrate amino acids. Factors affecting the degree of adaptation are biotin and substrate concen­trations, pH and strain differences. Deadaptation is pro­duced by excess biotin or the removal of substrate. The relation of adaptation to the low biotin effect is discussed.

The L-oxidase is involved in detoxification of cana­vanine. Strain differences in canavanine sensitivity are paralleled by certain qualitative differences in L-oxidase activity. Canavanine resistance is increased on low biotin. The relation of these observations to canavanine sensiti­vity and its genetic control is discussed.

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