title: Selective deamidation and enzymatic methylation of seminal ribonuclease.
abstract: Isoenzymatic forms alpha 2, alpha beta, and beta 2 of bovine seminal ribonuclease are generated by the transformation of beta-type into alpha-type subunit through deamidation of a single amide group [Di Donato, A., & D'Alessio, G. (1981) Biochemistry 20, 7232-7237]. The residue involved in this selective deamidation has been identified as Asn67. Deamidation occurs by formation of a cyclic imide intermediate involving the Gly at position 68. Opening of the cyclic imide may occur on either side of the nitrogen, generating both the normal alpha-aspartyl and an isoaspartyl residue at position 67. The alpha-carboxyl of the isoaspartyl residue is effectively methylated by bovine brain protein carboxylmethyltransferase.
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002417:Cattle; D019811:Hydroxylamine; D006898:Hydroxylamines / Q000494:pharmacology; D007527:Isoenzymes / Q000378:metabolism*; D046911:Macromolecular Substances; D008297:Male; D008745:Methylation; D010446:Peptide Fragments / Q000032:analysis; D012260:Ribonucleases / Q000378:metabolism*; D012661:Semen / Q000201:enzymology*; D014357:Trypsin
chemical_list: D006898:Hydroxylamines; D007527:Isoenzymes; D046911:Macromolecular Substances; D010446:Peptide Fragments; D019811:Hydroxylamine; D012260:Ribonucleases; D014357:Trypsin