PRODUCTION OF THE OOCYTE MATURATION-INDUCING SUBSTANCE OF STARFISH BYHEAT-TREATMENT OF S-ADENOSYLMETHIONINE

1-Methyladenine (1-MeA) has been identified as the oocyte maturation-i nducing substance (MIS) in starfish, but little is known about its bio synthesis. This study showed that starfish MIS activity was present in a reactant derived from S-adenosylmethionine (SAM) by heat treatment. In vitro MIS production was markedly dependent on the temperature of the SAM solution: it increased as the temperature was raised, and reac hed a plateau within 5 min upon boiling, although hardly only MIS was observed upon incubation below 20 degrees C. MIS production was also d ependent on the solution pH. Analyses by high-performance liquid chrom atography and thin-layer chromatography showed that the MIS was 1-MeA, though the maximum amount of 1-MeA obtained from SAM by boiling was o nly 0.3% of the initial SAM amount. Furthermore, use of S-[C-14-methyl ]SAM showed that a methyl group of 1-MeA was transferred from the SAM. Thus, it is possible that 1-MeA may be produced from SAM in vivo.