title: alpha-D-mannosidase forms in chicken liver.
abstract: Two forms (I and II) of alpha-D-mannosidase have been separated by ion-exchange chromatography on DEAE-cellulose from embryonic chicken liver. A third form (III), which is absent in embryos, was also separated from 4-day-old chickens. The optimum pH of form I is at pH 5.0. Form II is named "neutral" because it shows maximal activity at pH 6.5. The optimum pH of form III is 4.5. Forms I and III are heat-stable at 50 degrees C for 1 hr, whereas form II is very unstable under these conditions. Zn2+ and Mg2+ have been found to increase the alpha-D-mannosidase activity of forms I and II. In contrast, Co2+ increases mannosidase I activity and inhibits form II from 18-day-old embryos. alpha-Methyl-D-mannoside, N-acetyl-D-mannosamine and D-mannosamine were found to be inhibitors of both forms I and II. "Neutral" mannosidase was also inhibited by chloride. Competitive inhibition by D-mannose was also studied and Ki values are given.
mesh_terms: D000375:Aging; D000818:Animals; D002642:Chick Embryo; D002645:Chickens; D002852:Chromatography, Ion Exchange; D003035:Cobalt / Q000494:pharmacology; D004789:Enzyme Activation / Q000187:drug effects; D006863:Hydrogen-Ion Concentration; D007525:Isoelectric Focusing; D007700:Kinetics; D008099:Liver / Q000201:enzymology*; D008274:Magnesium / Q000494:pharmacology; D008361:Mannosidases / Q000037:antagonists & inhibitors / Q000145:classification / Q000302:isolation & purification*; D013696:Temperature; D015032:Zinc / Q000494:pharmacology; D043323:alpha-Mannosidase
chemical_list: D003035:Cobalt; D008361:Mannosidases; D043323:alpha-Mannosidase; D008274:Magnesium; D015032:Zinc