弗氏柠檬酸杆菌中乳糖转运系统的特性分析。

Characterization of the lactose transport system in Citrobacter freundii.

作者信息

Okazaki N, Tsuda M, Wilson T H, Tsuchiya T

机构信息

Department of Microbiology, Faculty of Pharmaceutical Sciences, Okayama University, Japan.

出版信息

Biol Pharm Bull. 1994 Jun;17(6):794-7. doi: 10.1248/bpb.17.794.

DOI:10.1248/bpb.17.794

PMID:7951140

Abstract

The lactose transport system of Citrobacter freundii was characterized. Both the lactose transport system and beta-galactosidase were induced with either lactose or isopropyl-beta-D-thiogalactopyranoside (IPTG), the latter being the better inducer. The Km values for methyl-beta-D-thiogalactopyranoside (TMG) transport and lactose transport were 0.61 mM and 1.1 mM, respectively, and the Vmax values were 53 nmol/min/mg cell protein and 12 nmol/min/mg cell protein, respectively. Thus, TMG is a better substrate than lactose. Thiogalactopyranoside (TDG) was a very potent competitive inhibitor. Neither Na+ nor Li+ had a significant effect on the TMG transport or the lactose transport. Proton/substrate cotransport (symport) via this system was observed.

摘要

对弗氏柠檬酸杆菌的乳糖转运系统进行了表征。乳糖转运系统和β-半乳糖苷酶均可被乳糖或异丙基-β-D-硫代半乳糖苷（IPTG）诱导，后者是更好的诱导剂。甲基-β-D-硫代半乳糖苷（TMG）转运和乳糖转运的Km值分别为0.61 mM和1.1 mM，Vmax值分别为53 nmol/分钟/毫克细胞蛋白和12 nmol/分钟/毫克细胞蛋白。因此，TMG是比乳糖更好的底物。硫代半乳糖苷（TDG）是一种非常有效的竞争性抑制剂。Na+和Li+对TMG转运或乳糖转运均无显著影响。观察到通过该系统的质子/底物共转运（同向转运）。