SUBSTRATE SPECIFICITY OF A GLUCOSE PERMEASE OF ESCHERICHIA COLI

Abstract

A study was made of D-galactose uptake by galactose-negative E. coli strain A (Weigle). Uptake probably occurred through a glucose-permease system, because D-glucose and a variety of nonmetabolizable glucose derivatives inhibited the accumulation of galactose and were themselves accumulated. D-Fructose did not inhibit galactose uptake. 6-Deoxy-D-galactose (D-fucose) was taken up by a different permease system. The glucose permease apparently favored pyranoses, and it required the 6-hydroxyl group of the substrate to a greater extent than any of the other hydroxyl groups. Although much of the absorbed glucose-permease substrate was recovered in the free form, a significant amount was recovered as the 6-phosphate ester. Depending on the conditions employed to study uptake the 6-phosphate ester could amount to as much as 60% of the absorbed galactose.