Subtilase

Subtilase is a term used for a large group of serine proteases known as subtilisin-like proteases. They are part of the peptidase family S8 and are characterized by a catalytic triad consisting of aspartate, histidine, and serine residues. Most subtilases are secreted enzymes that act on extracellular proteins, often with a preference for peptide bonds adjacent to hydrophobic residues. Many are calcium-dependent, which stabilizes their structure and can influence activity.

The subtilase family includes enzymes from bacteria, fungi, and plants, with substantial diversity in substrate specificity and environmental adaptation. The prototypical bacterial enzyme is subtilisin (subtilisin Carlsberg) from Bacillus species, used historically in laundry detergents and protein processing. Proteinase K, a widely used protease in molecular biology, is also considered subtilase-like. Plant genomes encode large repertoires of subtilase-related proteases (subtilase-like serine proteases, SBTs) involved in development, seed germination, defense, and hormone processing.

Biochemically, subtilases are single polypeptides synthesized as preproenzymes that contain an N-terminal signal peptide and a pro-domain; the pro-domain acts as an intramolecular chaperone and inhibitor until maturation. Activation occurs by autoproteolysis and removal of the pro-domain. The enzymes generally favor alkaline pH and require calcium binding for stability.

In addition to conventional proteolytic roles, the term subtilase appears in reference to the subtilase cytotoxin (SubAB) of certain pathogenic Escherichia coli, where SubA is a subtilase-family protease subunit that contributes to cytotoxicity. This usage is context-specific rather than denoting the housekeeping subtilases.