S. Fukui, A. Tai, R. Hochster
1965
Citations
0
Influential Citations
6
Citations
Journal
Journal of General and Applied Microbiology
Abstract
The biochemical conversion of saccharides to their corresponding 3-uloses was shown by several researchers (1, 2, 3, .4, 5), and the chemical structures of 3-ketoglucose, 3-ketosucrose, 3-ketotrehalose, 3-ketomaltose and 3-ketolactose were confirmed to be D-ribo-hexos-3-ulose, a-D-ribo-hexopyranosyl-3ulose-j3-D-f ructof rnaoside, a-D-ribo-hexos-3-ulose-(1--1)-a-n-glucopyranoside, D-ribo-hexos-3-ulose-(1-44)-a-D-glucopyranoside and D-xylo-hexos-3-ulose-D glucopyranoside, respectively (4, 5). With growing cells of Agrobacterium tume f aciens the rates of formation and subsequent utilization of the products from sucrose, trehalose, maltose and lactose were given in the previous paper (5). They show that following a lag period these disaccharides disappear and simulaneous accumulation of their corresponding glycoside-3-uloses takes place in the culture medium with high yield. In the course of studies on glycoside-3-ulose formation, the sequential utilization of substrates, when both sucrose and glucose are present, could be domonstrated with both resting and growing cells of Agr. tume f aciens (6). Moreover, we discovered the stereospecific, competitive inhibition of the enzymatic conversion of sucrose to 3-ketosucrose by D-glucose (7). This inhibitory effect was found only in intact cells and not in cell-free extracts. These findings give rise to the following speculation of the glucose effect : glucose may act as an inhibitor of the sucrose receptor site located on the cell surface. Actually, identical results were obtained in the kinetic studies on sucrose transport reaction, giving a Km value for sucrose of 2 x 10_3 M and a Ki value for glucose of 1.5x 10_6 M (8). Thus, clear explanation of the glucose inhibition can be shown by its high affinity for the site of sucrose uptake. The sucrose transport process in Agr. tume f aciens was characterized by uphill and energy dependency (9), so that it could be concluded the process is classified as an "ACTIVE ", according to the definition presented in the review of Cirillo (10). Regarding fermentation, conversion of substrate to product by growing cells, it can be divided into the following three steps : (1) entry of substrate