Exo-a-mannosidase

For degradation of the carbohydrate moiety of 50 mg ARS2 sample, 10 or 25 U exo-P-galactosidase were added and the mixture was incubated at 37°C for 18 hr 10 ml of 100 mM acetate buffer (pH 4.2) containing 25 U endo-P-1,4-galactanase or 1 mg crude endo-P-1,6-galactanase [43] were added and the mixture was incubated at 45°C for 48 hr. Fifty unit exo-a-mannosidase or 0.5 U endo-P-galactosidase in 50 mM potassium phosphate buffer (pH 6.0) at 37 °C for 18 h was also used. 

Cycloaddition reaction of nitrone (—)-(394) with dimethyl maleate D14 has been used for the synthesis of two new polyhydroxyl pyrrolizidines (687) and (688) (Schemes 2.293, 2.294). These compounds are analogs of alkaloids ros-marinecine and crotanecine, which were assayed for their inhibitory activities toward 22 commercially available glycosidase enzymes. One of them ((-)- a-epi-crotanecine) (—)-(688) is a potent and selective inhibitor of a-mannosidases (310). The reaction of (—)-(394) with dimethyl maleate gave a 9.6 6 1 mixture of cycloadducts (—)-(680), (+ )-(680), and (—)-(681), which arise from anti-exo,... 

Two structural examples of a new family, GH 125, of inverting metal-independent exo-a-l,6-mannosidases, from Clostridium perfringens and from S. pneumoniae, respectively, were recently reported. 1-Deoxymannojirimycin (11, Scheme 4) in the... 

Galactomannans and oligosaccharide fragments are susceptible to hydrolysis by a number of enzymes, including a-D-galactosidase90 (EC 3.2.1.22), /S-D-mannanase, exo-/3-D-mannanase,91 /3-D-mannosidase, and exo-/3-D-mannan mannobiohydrolase (EC 3.2.1.100).92 Early applications of enzymic... 

Proteins of a crude enzyme preparation obtained from the cultivation medium of the basidiomycete Phellinus abietis were separated by gel filtration and ion-exchange chromatography. The preparation contained a minimum of three enzymes capable of splitting a-D-mannosidic bonds a-D-mannosidase, exo-D-mannanase, and e/ido-D-mannanase, which were separated. Some properties of the D-mannanase complex of the crude enzyme preparation, and of a partially purified a-D-mannosidase, were examined. The D-mannanase complex exhibited two pH optima, its temperature optimum being 45 C. The pH optimum of purified a-D-mannosidase was at pH 5.0, the temperature optimum was at 60 °C the enzyme had a relatively high heat stability. The of a-D-mannosidase for 4-nitrophenyl a-D-mannopyranoside was 1.5xl0 M. Pure a-D-mannosidase did not split D-mannan. 

---