The first crystal structure of a family 45 glycoside hydrolase from a brown‐rot fungus, Gloeophyllum trabeum GtCel45A

Here we describe the first crystal structure of a beta‐1,4‐endoglucanase from a brown‐rot fungus, Gloeophyllum trabeum Gt Cel45A, which belongs to subfamily C of glycoside hydrolase family 45 (GH45). Gt Cel45A is ~ 18 kDa in size and the crystal structure contains 179 amino acids. The structure is refined at 1.30 Å resolution and R free 0.18. The enzyme consists of a single catalytic module folded into a six‐stranded double‐psi beta‐barrel domain surrounded by long loops. Gt Cel45A is very similar in sequence (82% identity) and structure to Pc Cel45A from the white‐rot fungus Phanerochaete chrysosporium . Surprisingly though, initial hydrolysis of barley beta‐glucan was almost twice as fast in Gt Cel45A as compared to Pc Cel45A.