Characterization of Nicotinamide Methyltransferase in Livers of Mice Bearing Ehrlich Ascites Tumors: Preferential Increase of Activity
作者:
Yasuo Hanazawa,
Kenichi Sato,
Namiko Kuroiwa,
Masako Ogawa,
Atsuko Kuriyama,
Mineko Asanagi,
Noriko Kato,
Yoichi Moriyama,
Keisuke Horitsu,
Shinji Fujimura,
期刊:
Tumor Biology
(Karger Available online 1994)
卷期:
Volume 15,
issue 1
页码: 7-16
ISSN:1010-4283
年代: 1994
DOI:10.1159/000217868
出版商: S. Karger AG
关键词: Nicotinamide methyltransferase;Tumor host liver;Enzyme characterization
数据来源: Karger
摘要:
There was a 2- to 7-fold increase in nicotinamide methyltransferase activity in the livers of mice and rats bearing seven different kinds of tumors compared with the respective control normal livers, while activity in the tumors themselves was hardly detectable. The activity in the liver started to increase markedly 3-7 days after i.p. transplantation of Ehrlich ascites tumors into the mice, maintaining a plateau up to death. Metabolic conversion of 14C-nicotinamide to 14C-N1methylnicotinamide was 3-fold higher in the slices of the ascites tumor host liver than in the normal liver, but the conversion to other radioactive metabolites was not significantly different. Nicotinamide methyltransferase was finally purified 20,000-fold with a yield of 4% from the cytosolic fraction of the ascites tumor host liver by means of five purification steps. At every purification step, only one enzyme fraction was detected. The enzyme finally isolated exhibited a single protein band in sodium dodecyl sulfate-polyacrylamide gel electrophoresis, with a molecular weight of 26,000. As for the compounds investigated, including the substrates for methyltransferases other than nicotinamide methyltransferase, only quinoline could be the substrate for enzyme activity. It is suggested that the increase in enzyme activity in the tumor host liver probably derived from the endogenous enzyme preexisting in the liver before tumor transplantation.
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