Gonad-stimulating substance, a hormonal peptide released from the nervous system of starfishes, acts on the ovary to produce 1-methyladenine, an inducer of oocyte maturation. Addition of methionine to the incubation mixture of ovarian fragments and gonad-stimulating substance enhanced the production of 1-methyladenine, whereas ethionine inhibited it. Incubation of ovarian tissue with methionine alone failed to produce 1-methyladenine. Use of a radioactive label showed that methionine is a methyl donor in the biosynthesis of 1-methyladenine, suggesting that gonad-stimulating substance is involved in the methylation process.
In starfish follicle cells 1‐methyladenine is produced under the influence of a gonad‐stimulating hormonal peptide (GSS). Since such production of the substance is enhanced by the addition of L‐methionine or S‐adenosylmethionine in vitro, the presence of methionine‐activating enzyme in the follicle cells of the starfish, Asterina pectinifera, was investigated. To detect enzyme activity, the enzyme was partially purified from the supernatant of the follicle‐cell homogenate by precipitation with ammonium sulfate followed by gel‐filtration on a Sephadex G‐150 column. Using such a preparation of the enzyme, the production of S‐adenosylmethionine from L‐methionine and adenosine triphosphate was clearly demonstrated by thin‐layer chromatography. GSS was found to exert no effect on the activity of the methionine‐activating enzyme. The hormonal peptide, GSS, is therefore considered to take part in some reaction other than this step in the formation of 1‐methyladenine.
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