Fowler A V, Smith P J
J Biol Chem. 1983 Sep 10;258(17):10204-7.
The active site-directed inhibitor 4-nitrophenyl-beta-D-galactopyranosylmethyltriazene, previously shown (Fowler, A. V., Zabin, I., Sinnott, M. L., and Smith, P. J. (1978) J. Biol. Chem. 253, 5283-5285) to alkylate methionine 502 in lacZ beta-galactosidase, was used to label the second naturally occurring beta-galactosidase of Escherichia coli (ebgo). The reagent was also used to label two mutant forms of the enzyme (ebga and ebgb) selected for enhanced lactase activity. In the case of ebgo and ebga, 75 and 85% of the label, respectively, was incorporated into a tryptic peptide which is homologous (38% identity) to residues 483-503 of the lacZ beta-galactosidase sequence. In the ebgo and ebga enzymes, a serine probably is alkylated. In the case of the ebgb enzyme, 61% of the label is found on a tryptic peptide homologous (69% identity) with residues 457-468 of the lacZ beta-galactosidase. In this peptide, a glutamic acid and a tyrosine residue are both alkylated.
活性位点导向抑制剂4-硝基苯基-β-D-吡喃半乳糖基甲基三氮烯，先前已证明（福勒，A.V.，扎宾，I.，辛诺特，M.L.，和史密斯，P.J.（1978年）《生物化学杂志》253，5283 - 5285）可使乳糖酶β-半乳糖苷酶中的甲硫氨酸502烷基化，该抑制剂被用于标记大肠杆菌的第二种天然存在的β-半乳糖苷酶（ebgo）。该试剂还被用于标记为提高乳糖酶活性而选择的该酶的两种突变形式（ebga和ebgb）。在ebgo和ebga的情况下，分别有75%和85%的标记掺入到一种胰蛋白酶肽中，该肽与乳糖酶β-半乳糖苷酶序列的483 - 503位残基同源（38%的同一性）。在ebgo和ebga酶中，可能是丝氨酸被烷基化。在ebgb酶的情况下，61%的标记位于一种与乳糖酶β-半乳糖苷酶的457 - 468位残基同源（69%的同一性）的胰蛋白酶肽上。在该肽中，一个谷氨酸残基和一个酪氨酸残基都被烷基化。
