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通过分子设计，确定Ｇｌｙ１３８为改善葡萄糖异构酶（ＧＩ）热稳定性的目标氨基酸。用双引物法对ＧＩ基因进行体外定点突变，构建了ＧＩ突变体Ｇ１３８Ｐ。含突变体的重组质粒ｐＴＫＤ－ＧＩＧ１３８Ｐ在Ｅ．ｃｏｌｉＫ３８菌株中表达。ＧＩＧ１３８Ｐ与野生型ＧＩ比较实验表明：（１）ＧＩＧ１３８Ｐ的热失活半衰期约是野生型ＧＩ的２倍；（２）ＧＩＧ１３８Ｐ的最适反应温度提高了１０～１２°Ｃ；（３）ＧＩＧ１３８Ｐ的比活与野生型ＧＩ相当。初步分析认为，Ｐｒｏ取代１３８位的Ｇｌｙ后，可能由于引入了一个吡咯烷环，该侧链刚好能够充填由于Ｇｌｙ１３８无侧链基团而留下的空洞，使蛋白质空间结构更具刚性，从而提高了酶的热稳定性。
Through molecular design, Gly138 was identified as the target amino acid to improve the thermostability of glucose isomerase (GI). The GI gene was subjected to site-directed mutagenesis using the double-primer method to construct GI mutant G138P. The recombinant plasmid pTKD-GIG138P containing the mutant is in E. coli. coliK38 strain expression. The comparison of GIG138P with wild-type GI showed that: (1) the half-life of thermal inactivation of GIG138P was about 2 times that of wild-type GI; (2) the optimum reaction temperature of GIG138P was increased by 10 ~ 12 ° C; (3) Live and wild-type GI quite. Preliminary analysis suggests that substitution of Pro by the Gly at position 138 may be due to the introduction of a pyrrolidine ring, which just fills the voids left by the unidentified Gly138 leaving the protein structure more rigid and thus increasing The enzyme’s thermal stability.