O'Connor C M, Clarke S
Biochem Biophys Res Commun. 1985 Nov 15;132(3):1144-50. doi: 10.1016/0006-291x(85)91926-6.
Protein carboxyl methyltransferase activity has been detected in extracts prepared from bacterial cells (Salmonella typhimurium), amphibian (Xenopus laevis) oocytes, and transformed mammalian cell lines. This activity appears to specifically recognize altered aspartyl residues based on the observation that the synthetic peptide L-Val-L-Tyr-L-Pro-L-isoAsp-Gly-L-Ala is a good methyl-accepting substrate for the methyltransferase activity, but that the corresponding peptide containing a normal L-aspartyl residue is not. These activities are similar to those of the previously described human erythrocyte and bovine brain enzymes which catalyze the formation of polypeptide D-aspartyl beta-methyl esters and L-isoaspartyl alpha-methyl esters. The wide distribution of these enzymatic activites suggest that the methylation of atypical proteins is an essential function in cells.
已在从细菌细胞（鼠伤寒沙门氏菌）、两栖动物（非洲爪蟾）卵母细胞和转化的哺乳动物细胞系制备的提取物中检测到蛋白质羧基甲基转移酶活性。基于合成肽L-缬氨酸-L-酪氨酸-L-脯氨酸-L-异天冬氨酸-L-甘氨酸-L-丙氨酸是甲基转移酶活性的良好甲基接受底物，但含有正常L-天冬氨酸残基的相应肽不是这一观察结果，这种活性似乎能特异性识别改变的天冬氨酰残基。这些活性与先前描述的催化形成多肽D-天冬氨酰β-甲酯和L-异天冬氨酰α-甲酯的人红细胞和牛脑酶的活性相似。这些酶活性的广泛分布表明非典型蛋白质的甲基化是细胞中的一项基本功能。
