β ‐Glucose 1‐phosphate‐interconverting enzymes in maltose‐ and trehalose‐fermenting lactic acid bacteria

Summary Maltose and trehalose catabolic pathways are linked through their common enzyme, β ‐phosphoglucomutase, and metabolite, β ‐glucose 1‐phosphate, in Lactococcus lactis . Maltose is degraded by the concerted action of maltose phosphorylase and β ‐phosphoglucomutase, whereas trehalose is assimilated by a novel pathway, including the recently discovered enzyme, trehalose 6‐phosphate phosphorylase, and β ‐phosphoglucomutase. In the present study, 40 strains of lactic acid bacteria were investigated for utilization of metabolic reactions involving β ‐glucose 1‐phosphate. All genera of the low G+C content lactic acid bacteria belonging to the clostridial subbranch of Gram‐positive bacteria were represented in the study. The strains, which fermented maltose or trehalose, were investigated for β ‐phosphoglucomutase, maltose phosphorylase and trehalose 6‐phosphate phosphorylase activity, as indications of maltose and trehalose catabolic pathways involving β ‐glucose 1‐phosphate interconversions. Eighty per cent of all strains fermented maltose and, of these strains, 63% were shown to use a maltose phosphorylase/ β ‐ phosphoglucomutase pathway. One‐third of the strains fermenting trehalose were found to harbour trehalose 6‐phosphate phosphorylase activity, and these were also shown to possess β ‐phosphoglucomutase activity. Mainly L. lactis and Enterococcus faecalis strains were found to harbour the novel trehalose 6‐phosphate phosphorylase/ β ‐phosphoglucomutase pathway. As lower β ‐glucose 1‐phosphate interconverting enzyme activities were observed in the majority of glucose‐cultivated lactic acid bacteria, glucose was suggested to repress the synthesis of these enzymes in most strains. Thus, metabolic reactions involving the β ‐anomer of glucose 1‐phosphate are frequently found in both maltose‐ and trehalose‐utilizing lactic acid bacteria.