Yahito Kotake

Anthranilic acid hydroxylation by rabbit-liver microsomes

Summary An enzyme (or enzymes) which converts anthranilic acid to 5-hydroxyanthrani-lic acid (anthranilate 5-hydroxylase) is associated with particles in rabbit liver secli-menting between 9000 × g for 30 min and 78 000 × g for 60 min. The optimal pH of the enzyme is near 6.8 when phosphate is used as a buffer. The Km value for the substrate is approx. 3.8 × 10−4 M. The enzyme requires reduced nicotinamide-adenine dinucleotide phosphate as a cofactor and the activity is inhibited by Cu2+, Ag+, metal-chelating agents (especially 8-hydroxyquinoline) and sulfhydryl inhibitors such as p-chloromercuribenzoate and α-chloroacetophenone. The stoichiometry of the enzyme has been established.

Complex formation between NADase and protein inhibitor from Mycobacterium butyricum

The importance of naturally occurring protein inhibitors in the control of enzyme activity for regulation of cellular metabolism has been suggested [l] and suitable protein inhibitors have been discovered for a number of enzymes. The existence of an inhibitor for NADase in cellfree extracts of Mycobacterium butyricum was first described by Kern and Natale [2]. This paper is concerned with evidence for the formation of a complex between NADase and its protein inhibitor obtained from M. butyricum. I

Studies on the Antioxidative Activities of Metabolites of Tryptophan

Try代謝産物の脂質に対する抗酸化性について, AOM, オーブン試験, DPPH法および重量法試験などで検討した。1) Tryならびにその代謝産物の抗酸化性は, AOM, オーブン試験の結果では3-OH-An. A. が最も高く, ついで, 5-OH-An. A, NAD, Alaなどで, An. A, Try, Ky. Aなどはほとんど認められず, Kyn, Try. Amでは, むしろ酸化促進性を示した。2) 5-OH-An. Aは低濃度 (0.003%) でも高い抗酸化性を示し, その抗酸化力は既存のBHAおよびTocとほとんど同じであった。3) 3-OH-An. A, 5-OH-An. A, Alaの三種混合系ならびにAla-NADの2種混合系の抗酸化力は, それぞれの単一系よりも高く, いわゆる相乗効果が認められた。4) Tryおよび5-OH-An. AにTocを混合させた場合, 抗酸化性に著しい相乗効果が認められた。5) 5-OH-An. Aの熱安定性は, 短時間の加熱時にはBHAおよびTocにくらべすぐれていたが, 長時間加熱ではむしろ劣った。