PERMEABILITY OF A MICROCOCCAL CELL TO MALTOSE AND SOME RELATED SUGARS

Cells of Micrococcus sp. ATCC No. 407 grown in glutamic acid medium were permeable to maltose, maltotriose, maltotetraose, maltopentaose, 3-ketomaltose, and β-methylmaltoside but not to glucose, α-methylglucoside, isomaltose, maltitol, cellobiose, sucrose, trehalose, or lactose. The results suggest that the uptake mechanism is constitutive and may be specific for sugars with α,1–4 linkages. The kinetics of maltose and maltotriose uptake are in accord with the sugars undergoing an initial combination with a site followed by a rate-limiting reaction. Maltotriose competitively inhibited maltose uptake, which suggests that the same site is used during uptake of these two sugars. Maltotriose was taken up at a greater rate than maltose, which suggests that the rate-limiting process during uptake is not diffusion but a reaction that proceeds faster with maltotriose than with maltose.