Abstract
The accumulation of glycine betaine (betaine) is one of the adaptive strategies for salt and drought stresses in plants. In the previous reports, we have shown the existence of two BADH genes (BBD1 and BBD2) in barley (Hordeum vulgare L.) and their corresponding proteins, peroxisomal (BBD1) and cytosolic (BBD2) BADHs. However, little information exists on the enzymatic properties of BBD1 and BBD2.
In this report, we investigated the substrate specificity of BBD1 and BBD2 with betaine aldehyde, 4-aminobutyraldehyde (AB-ald) and 3-aminopropionaldehyde (AP-ald). Enzymatic analyses indicated that the affinity of BBD2 for betaine aldehyde, a precursor of glycine betaine, was 1000-fold higher than that of BBD1. However, BBD1 catalyzed the oxidation of AB-ald and AP-ald as efficiently as BBD2 did.
These findings strongly suggest that BBD2 is mainly involved in glycine betaine synthesis in barley plants.
