Multiplicity of enzymatic functions in the CAZy AA3 family

Leander Sützl,Dietmar Haltrich,Roland Ludwig,Annabelle T Abrera,Georg Schütz,Christophe V F P Laurent

doi:10.1007/s00253-018-8784-0

Abstract

The CAZy auxiliary activity family 3 (AA3) comprises enzymes from the glucose-methanol-choline (GMC) family of oxidoreductases, which assist the activity of other AA family enzymes via their reaction products or support the action of glycoside hydrolases in lignocellulose degradation. The AA3 family is further divided into four subfamilies, which include cellobiose dehydrogenase, glucose oxidoreductases, aryl-alcohol oxidase, alcohol (methanol) oxidase, and pyranose oxidoreductases. These different enzymes catalyze a wide variety of redox reactions with respect to substrates and co-substrates. The common feature of AA3 family members is the formation of key metabolites such as H2O2 or hydroquinones, which are required by other AA enzymes. The multiplicity of enzymatic functions in the AA3 family is reflected by the multigenicity of AA3 genes in fungi, which also depends on their lifestyle. We provide an overview of the phylogenetic, molecular, and catalytic properties of AA3 enzymes and discuss their interactions with other carbohydrate-active enzymes.

Highlights

The Carbohydrate-Active enZYme (CAZy) database describes families of structurally related catalytic modules and domains of enzymes that degrade, modify, or create glycosidic linkages
The catalytic modules or enzymes in this database are grouped in families of glycoside hydrolases (GH), polysaccharide lyases (PL), carbohydrate esterases (CE), and glycosyltransferases (GT); in addition, the non-catalytic carbohydrate-binding
It is understood that the main chains of polysaccharides such as chitin, cellulose, or starch are cleaved by hydrolytic mechanisms and by oxidative reactions catalyzed by lytic polysaccharide monooxygenases (LPMO; (Beeson et al 2015))

Summary

Introduction

The Carbohydrate-Active enZYme (CAZy) database (http:// www.cazy.org/) describes families of structurally related catalytic modules and domains of enzymes that degrade, modify, or create glycosidic linkages. A comparison based on a phylogenetic inference using sequences of 58 biochemically characterized enzymes (Fig. 1) shows that family AA3 is further divided into four subfamilies: AA3_1 (including the flavodehydrogenase domains of cellobiose dehydrogenase, CDH), AA3_2 (aryl-alcohol oxidoreductases, both oxidases, AAO and dehydrogenases, AADH, and glucose 1-oxidases, GOx; here we included glucose 1-dehydrogenases, GDH, and pyranose dehydrogenases, PDH, based on their high-sequence similarities to the former two enzymes), AA3_3 (alcohol oxidases; AOx), and AA3_4 (pyranose oxidases, POx).

Results

Conclusion