MULTIPLE FORMS OF ALPHA-D-MANNOSIDASE IN HUMAN-PLASMA

The acidic α-D-mannosidase in human plasma closely resembles liver acidic α-D-mannosidase in its affinity for concanavalin A-Sepharose, molecular weight and resolution into multiple components on DEAE-cellulose. A combination of chromatography on concanavalin A-Sepharose and gel filtration on Sephadex G-200 and Sepharose 6B suggests that four forms of intermediate α-D-mannosidase, which differ either in their molecular weight or affinity for concanavalin A, exist in human plasma. A practical classification and nomenclature for the multiple forms of intermediate α-D-mannosidase in plasma based on molecular weight and affinity for concanavalin A is proposed. Multiple forms of intermediate α-D-mannosidase were also observed by ion-exchange chromatography on DEAE-cellulose, but there was not a simple correlation between these forms and those obtained with the other separation procedures. The form of intermediate α-D-mannosidase least abundant in plasma, approx. 7% of the activity, has very similar properties to the neutral α-D-mannosidase in human liver. In contrast, the other three forms of intermediate α-D-mannosidase, which account for over 90% of the activity do not appear to be present in liver, except perhaps in trace amounts.