Isolation and characterization of a (1 → 3)‐β‐glucan endohydrolase from germinating barley (Hordeum vulgare): amino acid sequence similarity with barley (1 → 3, 1 → 4)‐β‐glucanases

A (1 → 3)‐β‐glucan 3‐glucanohydrolase (EC 3.2.1.39) has been purified approx. 190‐fold from extracts of germinating barley. The enzyme has an apparent M r 32 000, a pI of 8.6, and a pH optimum of 5.6. Analysis of hydrolysis products released from the (1 → 3)‐β‐glucan, laminarin, shows that the enzyme is an endohydrolase. Sequence analysis of the 46 NH2‐terminal amino acids of the (1 → 3)‐β‐glucanase reveals 54% positional identity with barley (1 → 3,1 → 4)‐β‐glucanases (EC 3.2.1.73) and suggests a common evolutionary origin for these two classes of β‐glucan endohydrolases. The barley (1 → 3)‐β‐glucanase also exhibits significant similarity with a (1 → 3)‐β‐glucanase from tobacco.