β-Glucosidase 1A, Caldicellulosiruptor saccharolyticus (EC 3.2.1.21), is a glucosidase enzyme that acts on β1→4 glycosidic bonds linking two glucose or glucose-substituted molecules, such as cellobiose. As a member of the cellulase family, it contributes to the breakdown of cellulose and related polysaccharides. Specifically, it functions as an exocellulase with specificity for various β-D-glucosidic substrates, catalyzing the hydrolysis of terminal, non-reducing β-D-glucosidic residues to release glucose.