Methyl donor for 1-methyladenine biosynthesis in starfish ovarian follicle cells.
1-Methyladenine (1-MeAde), the oocyte maturation-inducing substance of starfish, is produced by ovarian follicle cells upon stimulation with a gonad-stimulating substance (GSS) released from radial nerves. It has been reported that a process of methylation is involved in GSS-induced 1-MeAde production by starfish ovarian follicle cells. The present study sought to identify a possible methyl donor for 1-MeAde biosynthesis in follicle cells of the starfish Asterina pectinifera. When isolated follicle cells were incubated with [methyl-(14)C]methionine (Met), there was an increase in the level of radiolabeled S-adenosylmethionine (SAM). After further incubation with GSS, the [methyl-(14)C]SAM level decreased, concomitant with a marked increase in radiolabeled 1-MeAde production. The amount of [methyl-(14)C]SAM consumed under the influence of GSS was similar to the amount of [methyl-(14)C]1-MeAde produced. Therefore, it is concluded that SAM is a methyl donor for 1-MeAde biosynthesis in starfish ovarian follicle cells. On the other hand, it is likely that the purine molecule of 1-MeAde is not derived from SAM but from ATP. 3-Isobutyl-1-methylxanthine, a potent inhibitor of cyclic AMP phosphodiesterase, also caused a reduction in the level of radiolabeled SAM following 1-MeAde production. This suggests that the methylation process of 1-MeAde biosynthesis in starfish ovarian follicle cells upon stimulation with GSS is mediated by a second messenger, cyclic AMP.
Mita
M
M
Department of Biology, School of Education, Waseda University, Shinjuku-ku, Tokyo, Japan. bio-mita@mn.waseda.ac.jp
Saneyoshi
M
M
Yoshikuni
M
M
Nagahama
Y
Y
D015056:1-Methyl-3-isobutylxanthine / Q000494:pharmacology; D000225:Adenine / Q000031:analogs & derivatives* / Q000096:biosynthesis; D000818:Animals; D002250:Carbon Radioisotopes; D002855:Chromatography, Thin Layer; D000242:Cyclic AMP / Q000378:metabolism; D006066:Gonads / Q000187:drug effects / Q000378:metabolism*; D007700:Kinetics; D008715:Methionine / Q000378:metabolism; D010726:Phosphodiesterase Inhibitors / Q000494:pharmacology; D012436:S-Adenosylmethionine / Q000378:metabolism; D015290:Second Messenger Systems; D013215:Starfish / Q000378:metabolism*
D002250:Carbon Radioisotopes; D010726:Phosphodiesterase Inhibitors; C008407:1-methyladenine; D012436:S-Adenosylmethionine; D008715:Methionine; D000242:Cyclic AMP; D000225:Adenine; D015056:1-Methyl-3-isobutylxanthine