@article { ISI:A1992HX16900032,
	title = {GLU-537, NOT GLU-461, IS THE NUCLEOPHILE IN THE ACTIVE-SITE OF (LAC-Z) BETA-GALACTOSIDASE FROM ESCHERICHIA-COLI},
	journal = {JOURNAL OF BIOLOGICAL CHEMISTRY},
	volume = {267},
	number = {16},
	year = {1992},
	month = {JUN 5},
	pages = {11126-11130},
	abstract = {The covalent intermediate formed during catalysis by the lac Z beta-galactosidase from Escherichia coli can be trapped by reaction of the enzyme with 2{\textquoteright},4{\textquoteright}-dinitrophenyl 2-deoxy-2-fluoro-beta-D-galactopyranoside, thereby inactivating the enzyme. Kinetic parameters for this inactivation process with the holo- and apoenzymes have been determined. The intermediate so formed turns over only very slowly (t1/2 = 11.5 h) resulting in reactivation of the enzyme. The nucleophilic amino acid involved has been identified as Glu-537 by using a tritium-labeled inactivator to label the enzyme, then cleaving the labeled protein into peptides and purifying and sequencing the labeled peptide. This residue is conserved in five homologous beta-galactosidases and is different from that (Glu-461) proposed to be the nucleophile (Herrchen, M., and Legler, G. (1984) Eur. J. Biochem. 138, 527-531) on the basis of affinity labeling studies with conduritol C cis-epoxide. A role for glutamic acid residue 461 as the acid/base catalyst is proposed and justified.},
	issn = {0021-9258},
	author = {GEBLER, JC and AEBERSOLD, R and Withers, SG}
}
