β-Amylase1 and β-amylase3 are plastidic starch hydrolases in Arabidopsis That Seem to Be Adapted for Different Thermal, pH, and stress conditions.

Starch degradation in chloroplasts requires β-amylase (BAM) activity, which is encoded by a multigene family. Of nine Arabidopsis (Arabidopsis thaliana) BAM genes, six encode plastidic enzymes, but only four of these are catalytically active. In vegetative plants, BAM1 acts during the day in guard cells, whereas BAM3 is the dominant activity in mesophyll cells at night.