title: Ovothiols, a family of redox-active mercaptohistidine compounds from marine invertebrate eggs.
abstract: We have previously reported a novel thiol compound, 1-methyl-N alpha,N alpha-dimethyl-4-mercaptohistidine, or ovothiol, present at high concentration in the eggs of the sea urchin Strongylocentrotus purpuratus [Turner, E., Klevit, R., Hopkins, P. B., & Shapiro, B. M. (1986) J. Biol. Chem. 261, 13056-13063]. Here we report two related compounds, 1-methyl-N alpha-methyl-4-mercaptohistidine, or ovothiol B, from the scallop Chlamys hastata, and 1-methyl-4-mercaptohistidine, or ovothiol A, from the starfish Evasterias troschelii. These two compounds, as well as the S. purpuratus compound now designated ovothiol C, were isolated from eggs or ovarian tissue by S-carboxymethylation with [3H]iodoacetic acid, ion-exchange chromatography and ion-pairing high-pressure liquid chromatography. The structures of S-(carboxymethyl)ovothiols A and B were determined by 1H NMR, and that of ovothiol A was confirmed by comparison with authentic methylhistidine samples after desulfuration with Raney nickel. In the ovary of each species, the predominant methylation form of ovothiol accounts for at least 80% of the total 4-mercaptohistidine. The ovothiol concentration of the ovary far exceeds that of the testis or somatic tissues. The ovothiol C content of unfertilized S. purpuratus eggs is 1.14 mumol/10(6) eggs, equivalent to approximately 4.3 mM average concentration; the glutathione (GSH + GSSG) content is 0.9 mumol/10(6) eggs. In this species, high ovothiol levels persisted for the first 2 weeks of embryonic development. Ovothiol and glutathione account for virtually all of the trichloroacetic acid soluble-SH groups in the egg; these results are compared to several previous studies.(ABSTRACT TRUNCATED AT 250 WORDS)
mesh_terms: D000603:Amino Acids, Sulfur / Q000032:analysis / Q000302:isolation & purification / Q000502:physiology*; D000640:Amitrole / Q000494:pharmacology; D000818:Animals; D002851:Chromatography, High Pressure Liquid; D005260:Female; D005307:Fertilization in Vitro; D006861:Hydrogen Peroxide / Q000378:metabolism / Q000633:toxicity; D007461:Iodoacetates / Q000494:pharmacology; D019807:Iodoacetic Acid; D009682:Magnetic Resonance Spectroscopy; D008297:Male; D008762:Methylhistidines; D008974:Mollusca / Q000201:enzymology*; D009247:NADH, NADPH Oxidoreductases / Q000378:metabolism; D019255:NADPH Oxidases; D010063:Ovum / Q000032:analysis*; D010544:Peroxidases / Q000502:physiology; D013215:Starfish / Q000201:enzymology*; D014018:Tissue Distribution
chemical_list: D000603:Amino Acids, Sulfur; D007461:Iodoacetates; D008762:Methylhistidines; C050085:ovothiol C; D006861:Hydrogen Peroxide; D010544:Peroxidases; D009247:NADH, NADPH Oxidoreductases; D019255:NADPH Oxidases; C022709:superoxide-forming enzyme; D019807:Iodoacetic Acid; D000640:Amitrole