Comparative Physical, Kinetic and Immunologic Properties of the Acidic and Neutral α-D-Mannosidase Isozymes from Human Liver

Abstract

Human α-mannosidases A, B and C were partially purified from liver by conventional and affinity chromatographic procedures. The kinetic, physical and immunologic properties of the A, B and C isozymes were determined including pH optima, K(m), effects of various inhibitors and activators, thermal stabilities, electrophoretic mobilities, native molecular weights and antigenic relationships. By gel filtration, the apparent native molecular weights were 240,000, 300,000 and 420,000 for the A, B and C isozymes, respectively. By polyacrylamide gel electrophoresis, the A and B isozymes had native molecular weights of approximately 150,000 and appeared to be charge isomers. Antibodies to the purified A and B isozymes were produced; cross-reactivity between the A and B isozymes against anti-A and anti-B immune sera were observed by double immunodiffusion and immunoprécipitation. In contrast, no reactivity of the C isozyme was detected with either immune serum. Based on these studies, models are presented for the molecular interrelationship of α-mannosidases A and B.

Glycolipid and Glycoprotein Degradation

“…These results were confirmed by cellulose acetate electrophoresis (5 18). a-Mannosidases A and B have identical pH optima and kinetic constants and seem to be differently glycosylated forms of the same enzyme (519). Form B can be converted into form A by treatment with sialidase (520,521) and both forms are immunochemically identical (519).…”

“…The activity can be restored immediately by the addition of excess zinc. Thus, the loss of Zn2' during purification may in some cases account for the poor recoveries [e.g., see (521)l and differences in purity and in incubation conditions may explain controversial results on ZnZ + requirement of the enzyme (519,(522)(523)(524)526,527,541). In the presence of 1-mM Zn" , a-mannosidase is stable at 65"C, pH 6.0 for at least 1 h (537).…”

Characterization of α‐mannosidase in feline mannosidosis

“…Figure 4 pH-Activity profile of a-mannosidase in subcellular fractions of liver from a control cat. Specific activity corresponding to 100% activity at the optimal pH for each fraction is indicated in the figure DISCUSSION Three types of mammalian ct-mannosidases have been described (Dewald and Touster, 1973;Philips et al, 1974Philips et al, , 1975Shoup and Touster, 1976;Opheim and Touster, 1978;Hirani and Winchester, 1979;Grabowski et al, 1980;Bischoff and Kornfeld, 1983). They are structurally and genetically distinct.…”

“…Figure 5 Heat inactivation pattern of ct-mannosidase in subcellular fractions of liver from a control cat studied at 51°C for various periods of time at pH4.0 (A) and pH5.5 (B) Philips et al, 1975;Grabowski et al, 1980), and three forms of Golgi mannosidase, Ia, Ib and II (Tulsiani et al, 1977(Tulsiani et al, , 1982Kornfeld, 1978, 1979;Harpaz and Schachter, 1980) can further be separated as multiple forms by chromatography or centrifugation. The properties of various forms of (~-mannosidases have been reviewed by Winchester (1984).…”

Characterization of the Mutant N-Acetylglucosaminylphosphotransferase in I-Cell Disease and Pseudo-Hurler Polydystrophy: Complementation Analysis and Kinetic Studies

“…Hexosaminidases A and B, and a-mannosidase B were purified from human placenta by affinity chro matography procedures as described [19][20][21][22]. Bovine liver ß-glucuronidase, type B-10, was obtained from Sigma Chemical Co. (St. Louis, Mo., USA).…”