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Glucooligosaccharide oxidase from Acremonium strictum was screened for potential applications in oligosaccharide acid production and carbohydrate detection. This protein is a unique covalent flavoenzyme which catalyzes the oxidation of a variety of carbohydrates with high selectivity for cello-and maltooligosaccharides. Kinetic measurements suggested that this enzyme possesses an open carbohydrate-binding groove, which is mainly composed of two glucosyl-binding subsites. The encoding gene was subsequently cloned, and one intron was detected in the genomic DNA. Large amounts of active enzymes were expressed in Pichia pastoris, with a yield of 300 mg per liter medium. The protein was predicted to share structural homology with plant cytokinin dehydrogenase and related flavoproteins that share a conserved flavin adenine dinucleotide (FAD)-binding domain. The closest sequence matches are those of plant berberine bridge enzyme-like proteins, particularly the characteristic flavinylation site. Unexpectedly, mutation of the putative FAD-attaching residue, H70, to alanine, serine, cysteine, and tyrosine did not abolish the covalent FAD linkage and had little effect on the K m . Instead, the variants displayed k cat values that were 50-to 600-fold lower, indicating that H70 is crucial for efficient redox catalysis, perhaps through modulation of the oxidative power of the flavin.Sugar oxidases and dehydrogenases that catalyze the oxidation of glucose and other carbohydrates into the corresponding lactones are widely distributed in nature. These enzymes have received great attention as potential diagnostic reagents and industrial biocatalysts. For example, glucose oxidase (GOX) is widely used in analytical biochemistry and in the food industry (21,22). A search of the BRENDA enzyme database (23) revealed that most of these enzymes are specific for a variety of mono-and disaccharides, and only a few enzymes exhibit high specificity with oligosaccharides. The latter enzymes include galactose oxidase, cellobiose dehydrogenase (CDH), and glucooligosaccharide oxidase (GOOX). GOOX from Acremonium strictum was identified from sugar oxidase-producing microorganisms with the aim of identifying enzymes with potential applications in oligosaccharide acid production and alternative carbohydrate assays (16).GOOX is a monomeric glycoprotein with a covalently linked flavin adenine dinucleotide (FAD) (16). It catalyzes the oxidization of a variety of carbohydrates with concomitant reduction of molecular oxygen to hydrogen peroxide. Screening of 30 monosaccharides and derivatives of these compounds showed that D-glucose is the only good substrate. In terms of the disaccharides, maltose, cellobiose, and lactose with reducing-end glucosyl residues linked by an ␣ bond or ␤-1,4 bonds are good substrates, whereas disaccharides containing other linkage types are not. Moreover, GOOX can react with maltooligosaccharides composed of ␣-1,4-linked D-glucopyranosyl residues (up to at least seven units); hence, the name of this novel oxidase. The broad...

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An extracellular alkaline lipase of alkalophilic Pseudomonas pseudoalcaligenes F-111 was purified to homogeneity. The apparent molecular weight determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis was 32,000, and the isoelectric point was 7.3. With p-nitrophenyl esters as its substrates, the enzyme shows preference for C 12 acyl and C 14 acyl groups. It was stable in the pH range of 6 to 10, which coincides with the optimum pH range.