In this sense, "alpha-glucosidase" can encompass a wide range of enzyme activitiess, differing by the linkage of their terminal (1→3, 1→4, or 1→6), the specific identity of their substrate (sucrose, maltose, or starch), among other aspects.

It requires the linkage to be 1→4, and the preferred substrate to be smaller oligosaccharides (as opposed to larger polysaccharides like starch: alpha-amylase would otherwise be included).

Human genes that produce enzymes with activities specified by this EC number include:[8] Synonyms mentioned by the Commission include maltase, glucoinvertase, glucosidosucrase, maltase-glucoamylase, α-glucopyranosidase, glucosidoinvertase, α-D-glucosidase, α-glucoside hydrolase, α-1,4-glucosidase, α-D-glucoside glucohydrolase.

The substrate selectivity of α-glucosidase is due to subsite affinities of the enzyme's active site.

[11] The gene coding for human lysosomal α-glucosidase is about 20 kb long and its structure has been cloned and confirmed.