Ramakrishnan S, Sulochana K N, Punitham R
Biochemistry Research Department, Vision Research Foundation, Sankara Nethralaya, Chennai, India.
Indian J Biochem Biophys. 1997 Dec;34(6):518-23.
The amino acids lysine, glycine, alanine, glutamate and aspartate formed adducts with galactose at physiological pH and temperature as shown by incorporation of U[14C] galactose. The percentage of galactose reacting with lysine, glycine, alanine, glutamate and aspartate was 4.5 to 7.8, 7.9 to 10.8, 3.2 to 4.6, 2.8 to 4.8 and 3 to 5.2, respectively. Studies with lysine showed that the extent of glycation of the free amino acid increased with time. Incubation of lens homogenate with galactose, effected glycation of proteins. Addition of lysine in concentrations of 5 and 10 mM to equimolar concentrations of galactose decreased the glycation of lens proteins by 64% to 71%; glycine, alanine, glutamate and aspartate decreased glycation by 23 to 68%, 32 to 61%, 35 to 56% and 26 to 61% respectively. Under similar conditions, glycine reacts to a greater extent than lysine, alanine, glutamic and aspartic acids. However, lysine was more effective than glycine, alanine, aspartic and glutamic acids in decreasing glycation of lens proteins by galactose. The decrease of glycation with added lysine increased with time. In general increase of amino acid concentration rather than that of sugar augmented the decrease of glycation of lens proteins.
如掺入U[14C]半乳糖所示，赖氨酸、甘氨酸、丙氨酸、谷氨酸和天冬氨酸在生理pH值和温度下与半乳糖形成加合物。与赖氨酸、甘氨酸、丙氨酸、谷氨酸和天冬氨酸反应的半乳糖百分比分别为4.5%至7.8%、7.9%至10.8%、3.2%至4.6%、2.8%至4.8%和3%至5.2%。对赖氨酸的研究表明，游离氨基酸的糖基化程度随时间增加。晶状体匀浆与半乳糖一起孵育会导致蛋白质糖基化。向等摩尔浓度的半乳糖中添加浓度为5 mM和10 mM的赖氨酸，可使晶状体蛋白的糖基化降低64%至71%；甘氨酸、丙氨酸、谷氨酸和天冬氨酸分别使糖基化降低23%至68%、32%至61%、35%至56%和26%至61%。在类似条件下，甘氨酸的反应程度大于赖氨酸、丙氨酸、谷氨酸和天冬氨酸。然而，在降低半乳糖对晶状体蛋白的糖基化方面，赖氨酸比甘氨酸、丙氨酸、天冬氨酸和谷氨酸更有效。添加赖氨酸后糖基化的降低随时间增加。一般来说，氨基酸浓度的增加而非糖浓度的增加会增强晶状体蛋白糖基化的降低。
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