Murphy J E, Kantrowitz E R
Department of Chemistry, Merkert Chemistry Center, Boston College, Chestnut Hill, Massachusetts 02167.
Mol Microbiol. 1994 May;12(3):351-7. doi: 10.1111/j.1365-2958.1994.tb01024.x.
Mammalian alkaline phosphatases are 20-30-fold more active than the corresponding bacterial enzymes even though their amino acid sequences are 25-30% absolutely conserved. In the active-site region there are two noticeable differences between the sequences of the bacterial and mammalian enzymes. In the Escherichia coli enzyme positions 153 and 328 are Asp and Lys, respectively, but in the mammalian enzymes His is observed at both of these positions. Site-specific mutagenesis, genetic and X-ray crystallographic data, which will be summarized here, suggest that the His substitutions at positions 153 and 328 are primarily responsible for the differences in properties between the bacterial and mammalian alkaline phosphatases.
哺乳动物碱性磷酸酶的活性比相应的细菌酶高20至30倍，尽管它们的氨基酸序列有25%至30%的绝对保守性。在活性位点区域，细菌和哺乳动物酶的序列存在两个明显差异。在大肠杆菌酶中，第153位和第328位分别是天冬氨酸和赖氨酸，但在哺乳动物酶中这两个位置都是组氨酸。本文将总结的定点诱变、遗传学和X射线晶体学数据表明，第153位和第328位的组氨酸取代主要导致了细菌和哺乳动物碱性磷酸酶之间性质的差异。
