Characterisation of class I and II α-mannosidases from Drosophila melanogaster

Homology searches indicated that up to five class I α-mannosidases (glycohydrolase family 47) and eight class II α-mannosidases (glycohydrolase family 38) are encoded by the fruitfly (Drosophila melanogaster) genome. Selected example mannosidases were expressed in secreted form using the yeast Pichia pastoris. A number of characteristics of these enzymes were determined with p-nitrophenyl-α-mannoside as substrate; particularly striking were the low optima (pH 5) of three class II mannosidases most closely related to known lysosomal mannosidases and the distinct Co(II)-requirement of a mannosidase previously named ManIIb. Some of the recombinant mannosidases were demonstrably active towards oligomannosidic glycans, specifically, the Co(II)-requiring ManIIb, two 'acidic' mannosidases and the class I mas-1 mannosidase. Other than previous characterisations of the well-known Golgi mannosidase II, this is the first study summarising various properties of recombinant mannosidases from the fruitfly.