COMPARATIVE BIOCHEMISTRY OF A CYTOSOLIC ARTIODACTYL GLYCOSIDASE

Artiodactyls possess abundant neutral glycosidase activity in liver, k idney and intestine, This enzyme is cytosolic and displays a more neut ral pH optimum, more acidic isoelectric point and broader substrate ra nge than the corresponding acidic beta-galactosidases. The neutral gly cosidases were more thermolabile than the respective acidic beta-galac tosidases and displayed a relative molecular mass approximating 60 kDa . This isozyme appeared to bca minor species in both rat and dog liver . The porcine enzyme was studied in more detail. Porcine neutral glyco sidase activity was detected in 45-day gestational fetuses in both liv er and kidney but not brain. Fetal kidney activities were about half t hose observed in adult kidney extracts. Porcine neutral glycosidase wa s immunologically distinct from acidic beta-galactosidase and was immu nologically similar to the corresponding isozymes from deer, ovine and bovine liver. Porcine neutral glycosidase was moderately inhibited by D-galactonic acid gamma-lactone and strongly inhibited by D-gluconic acid delta-lactone; however, acidic beta-galactosidase was not inhibit ed by the delta-lactone. Inhibition by the gamma-lactone was competiti ve for both enzymes. 4-Methylumbelliferyl-beta-D-galactoside, glucosid e and -xyloside competed for the same active site. A polymorphism for fast- and slow-migrating isozymes of porcine neutral glycosidase was o bserved, which appeared to be under genetic control. (C) 1997 Elsevier Science Inc.