n. (context enzyme English) Any of various enzymes that break down pectin.
Pectinase is an enzyme that breaks down pectin, a polysaccharide found in plant cell walls. Commonly referred to as pectic enzymes, they include pectolyase, pectozyme, and polygalacturonase, one of the most studied and widely used commercial pectinases. It is useful because pectin is the jelly-like matrix which helps cement plant cells together and in which other cell wall components, such as cellulose fibrils, are embedded. Therefore, pectinase enzymes are commonly used in processes involving the degradation of plant materials, such as speeding up the extraction of fruit juice from fruit, including apples and sapota. Pectinases have also been used in wine production since the 1960s. The function of pectinase in brewing is twofold, first it helps break down the plant (typically fruit) material and so helps the extraction of flavours from the mash. Secondly the presence of pectin in finished wine causes a haze or slight cloudiness. Pectinase is used to break this down and so clear the wine.
They can be extracted from fungi such as Aspergillus niger. The fungus produces these enzymes to break down the middle lamella in plants so that it can extract nutrients from the plant tissues and insert fungal hyphae. If pectinase is boiled it is denatured (unfolded) making it harder to connect with the pectin at the active site, and produce as much juice.
Pectinases are also used for retting. Addition of chelating agents or pretreatment of the plant material with acid enhance the effect of the enzyme.