alpha-Amylase is an important amylolytic enzyme participating in hydrolysis of starch, the most common carbohydrate in nature. Compared to plant and animal origins, microbial alpha-amylase is the most popular source of industrial alpha-amylase. As such, high productive and favourable alpha-amylases for wider range of applications are highly sought after demands. The expression of alpha-amylase is regulated by its structural gene, amyR, DegU-P, PrsA lipoprotein, cutinase and other similar flanking genes, components of gene expression regulatory systems, molecular chaperones and enzymes. Moreover, the characteristics of alpha-amylase are closely related to the structures of constitutive domains and conserved regions, particularly the functional regions such as Ca2+-binding sites, non-catalytic carbohydrate-binding modules and surface-binding sites. Recent production of alpha-amylase based on genetic engineering and academic researches focused on mechanisms of catalysis greatly benefit from these biomolecular studies. Despite rapid developments, no reviews have systematically summarized these fundamental biomolecular studies. This review outlines microbial alpha-amylase at gene and structure levels by covering these significant aspects. The computer analytical tools are also reported, especially frequently used databases. A deeper understanding of the biomolecular basis of microbial alpha-amylase will significantly pave greater opportunities for industrial alpha-amylase and open our minds towards its related or even other enzymes. (C) 2016 Elsevier Ltd. All rights reserved.