Specificity and kinetic parameters of recombinant Microdochium nivale carbohydrate oxidase

A new carbohydrate oxidase from Microdochium nivale heterologously expresse d in Aspergillus oryzae (rMnO) has been characterized. The carbohydrate oxi dase is a flavoenzyme which oxidizes glucose and other mono- or oligosaccha rides. It shows a broad substrate specificity towards carbohydrates reactin g with aldoses in the I-position. The rMnO oxidizes the beta -form of D-glu cose, and the product of D-glucose oxidation is D-gluconic acid. The mechanism of carbohydrate oxidation by oxygen and artificial electron a ccepters has been described by a ping-pong scheme. Compared to Aspergillus niger glucose oxidase (GOx) the reactivity of rMnO at pH 7.0 is significant ly lower; k(cat) is 20, k(ox) 11 and k(red) 22 times less, using oxygen as electron acceptor. Also with other two electron accepters, like DPIP, the a ctivity is low. However, compared to oxygen the rMnO shows 2-10 times highe r activity towards some artificial single electron accepters (AAs). The enz yme activity increases at higher ionic strength of the solution, if positiv ely-charged AAs are used. The high activity towards AAs and low rate for oxygen as well as broad spec ificity to carbohydrates indicates that rMnO may have some advantages compa red to the most used GOx in connection with enzyme use for analytical devic es and for biotechnological purposes. (C) 2001 Elsevier Science B.V. All ri ghts reserved.