Convertase

Convertase is a term used in biochemistry and immunology to describe an enzyme that catalyzes the transformation of a substrate into a different form, usually by proteolytic cleavage. In many contexts, convertases activate inactive precursor proteins by processing them into their mature, functional forms. The word is most often applied to two distinct classes: proprotein convertases and complement convertases.

Proprotein convertases are a family of subtilisin-like serine proteases that activate secreted or membrane-bound proteins by cleaving at specific multibasic motifs. Members include furin and several prohormone convertases (for example, PC1/3, PC2). They operate mainly in the secretory pathway, such as the endoplasmic reticulum and Golgi, and are responsible for activating hormones, growth factors, receptors, and various enzymes. Disruption of proprotein convertase activity can affect endocrine signaling, development, and pathogen life cycles, and is an area of interest for therapeutic targeting.

Complement convertases are enzyme complexes that regulate the innate immune response. The classical and lectin pathways produce the C3 convertase C4b2a, while the alternative pathway forms C3 convertase C3bBb. These convertases cleave the complement component C3 into C3a and C3b, and, with additional components, generate C5 convertases that cleave C5. This cascade leads to opsonization, inflammation, and the membrane attack reaction. It is tightly regulated by various cofactors and inhibitors to prevent damage to host tissue.

In summary, convertases are enzymes that activate or process substrates through proteolytic cleavage, with notable examples in protein maturation and complement system activation.