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G W Lin

Publications and source records attributed to G W Lin.

23 records · Page 2Linked to original sources
PubMed1977

Partial purification and characterization of tumor and liver S-adenosylmethionine synthetases.

The S-adenosylmethionine synthetase activities of rat liver and Novikoff ascites tumor have been partially purified and characterized by chromatographic behavior, kinetic analysis, sulfhydryl dependency, and response to inhibitors. We have shown that the tumor contains a single form of the enzyme, with a Km (methionine) of 21 muM, and that the liver contains two isofunctional forms, a minor form with a Km (methionine) of 21 muM, as well as a major form with a Km of 1 mM. The tumor contained more of the low Km form of the enzyme than the liver, although the total enzyme activity of liver (measured at high substrate concentrations) exceeded that of the tumor severalfold. The tumor enzyme also corresponded to the minor form of liver enzyme in elution position from Sephadex G-150 and diethylamino-ethyl cellulose, and both had a Km (adenosine 5'-triphosphate) of 0.14 mM. The tumor enzyme differed from the major form of the liver enzymes in elution position, and the Km (adenosine 5'-triphosphate) for the latter was 1.5 mM. In contrast to the major liver enzyme, the tumor enzyme did not appear to require sulfhydryl agents for the activity to be detected, was inhibited by S-adenosylmethionine, and was inhibited to a greater degree by tripolyphosphate. It is suggested that the two forms of the enzyme are involved in the production of S-adenosylmethionine for different biological functions, and their different properties may allow selective inhibition of tumor growth by chemotherapeutic agents.

Animals↗
PubMedDate not supplied

Maternal-fetal folate transfer: effect of ethanol and dietary folate deficiency.

The effects of acute ethanol treatment and dietary folate deficiency on maternal-fetal folate transfer were studied to asses the hypothesis that the potentiation of ethanol's toxic effect on the fetus during ongoing folate deficiency was due to the impairment of folate transfer. Sprague-Dawley rats were fed either a folate-deficient diet (0.2 mg/kg) or a folate-sufficient diet (2 mg/kg) for an average of 11 weeks before pregnancy and continued until gestation day 11 when they were sacrificed. On gestation day 11, pregnant rats were treated with either ethanol (2.5 g/kg body weight) or isocaloric sucrose (control) followed by an intravenous administration of 3H-folate (2 muCi/100 g body weight) at 120 minutes. At 210 minutes, maternal blood and feto-placental tissues were removed for radioactivity measurement. Folate status and ethanol treatment had no effect on the distribution of 3H-folate in maternal circulation. However, contrary to the hypothesis, the uptake of 3H-folate by feto-placental tissues was increased in folate deficiency and by ethanol treatment, indicating that folate transfer was not impaired by the ethanol treatment. Other possibilities are discussed.

Animals↗