4-O-beta-D-mannosyl-D-glucose phosphorylase (, mannosylglucose phosphorylase) is an enzyme with systematic name 4-O-beta-D-mannopyranosyl-D-glucopyranose:phosphate alpha-D-mannosyltransferase. This enzyme catalyses the following chemical reaction
This enzyme forms part of a mannan catabolic pathway in the anaerobic bacterium Bacteroides fragilis NCTC 9343.