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标题：MULTIPLE FORMS OF ARYL SULFOTRANSFERASE FOR ACETAMINOPHEN SULFATE CONJUGATION IN RAT LIVER CYTOSOL
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作者：TAKASHI MIZUMA ; HIROSHI ARAYA ; MASAHIRO HAYASHI 等
期刊名称：Biological and Pharmaceutical Bulletin
印刷版ISSN：0918-6158
电子版ISSN：1347-5215
出版年度：1984
卷号：7
期号：10
页码：784-789
DOI：10.1248/bpb1978.7.784
出版社：The Pharmaceutical Society of Japan
摘要：The multiplicity of aryl aulfotransferase (phenol sulfotransferase, PST) in acetaminophen (APAP) sulfate conjugation was studied in rat liver cytosol. The sulfation rate showed the optimal pH of about 9 similar to that in the phenolic monoamine sulfation. And another optimal pH of about 6.4 was found at the higher APAP concentration such as 16 mM, suggesting the existence of the PST multiplicity in the APAP sulfation. The effect of thermal treatment at various temperatures, 37 to 41°C, showed that PST catalyzing the sulfation at the lower APAP concentration (about less than 1 mM) is more thermolabile and has the lower K_m for APAP than at the higher APAP concentration. The APAP sulfation at μM order APAP in the presence of p-nitrophenol (PNP) was shown to be decreased by the substrate inhibition of PNP to PST. Consequently it is considered the sulfation at the lower APAP concentration (μM order) is mainly catalyzed by the thermolabile PST with the lower K_m for APAP, and at the higher APAP concentration the thermostable PST with the higher K_m partially contributes to the sulfation.
关键词：Michaelis constant