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Pectinase
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Pectinase
Pectinases are a group of enzymes that breaks down pectin, a polysaccharide found in plant cell walls, through hydrolysis, transelimination and deesterification reactions. Commonly referred to as pectic enzymes, they include pectolyase, pectozyme, and polygalacturonase, one of the most studied and widely used[citation needed] 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 flavors 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.
Pectinases 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.
Pectinase is a generic term used for a group of enzymes that catalyse the degradation of pectin by hydrolysis, trans-elimination, as well as de-esterification reactions. The degradation of pectic polymers is mainly caused by exo- and endo-polygalacturonases (exo- and endo-PGs), pectate and pectin lyases (PLs), pectin methylesterase (PME) and acetylesterase (PAE), β-galactosidase (β-Gal), and α-L-arabinofuranosidase (α-L-Af), among others.
The following table shows a summary of enzymes involved in pectin degradation. HG-PUL = homogalacturonan polysaccharide utilization loci; RG-I PUL = rhamnogalacturonan I polysaccharide utilization loci.
All pectinase enzyme structures include a prism-shaped right-handed cylinder made up of seven to nine parallel β-helices. The three parallel β-helices that create the prism shape of the structure are referred to as PB1, PB2 and PB3, with PB1 and PB2 creating an antiparallel β and PB3 sitting perpendicularly to PB2. All substrate binding sites of the various esterases, hydrolases, and lyases are located on an outer cleft of the central parallel β-helix structure between protruding loops on the structure and PB1.
As with all enzymes, pectinases have an optimum temperature and pH at which they are most active. For example, a commercial pectinase might typically be activated at 45 to 55 °C and work well at a pH of 3.0 to 6.5.
Pectinases depolymerise pectin through hydrolysis, trans-elimination and deesterification reaction processes, breaking down the ester bond that holds together the carboxyl and methyl groups in pectin.
Endo-polygalacturonase progresses through a reaction along the following pathway:
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Pectinase
Pectinases are a group of enzymes that breaks down pectin, a polysaccharide found in plant cell walls, through hydrolysis, transelimination and deesterification reactions. Commonly referred to as pectic enzymes, they include pectolyase, pectozyme, and polygalacturonase, one of the most studied and widely used[citation needed] 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 flavors 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.
Pectinases 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.
Pectinase is a generic term used for a group of enzymes that catalyse the degradation of pectin by hydrolysis, trans-elimination, as well as de-esterification reactions. The degradation of pectic polymers is mainly caused by exo- and endo-polygalacturonases (exo- and endo-PGs), pectate and pectin lyases (PLs), pectin methylesterase (PME) and acetylesterase (PAE), β-galactosidase (β-Gal), and α-L-arabinofuranosidase (α-L-Af), among others.
The following table shows a summary of enzymes involved in pectin degradation. HG-PUL = homogalacturonan polysaccharide utilization loci; RG-I PUL = rhamnogalacturonan I polysaccharide utilization loci.
All pectinase enzyme structures include a prism-shaped right-handed cylinder made up of seven to nine parallel β-helices. The three parallel β-helices that create the prism shape of the structure are referred to as PB1, PB2 and PB3, with PB1 and PB2 creating an antiparallel β and PB3 sitting perpendicularly to PB2. All substrate binding sites of the various esterases, hydrolases, and lyases are located on an outer cleft of the central parallel β-helix structure between protruding loops on the structure and PB1.
As with all enzymes, pectinases have an optimum temperature and pH at which they are most active. For example, a commercial pectinase might typically be activated at 45 to 55 °C and work well at a pH of 3.0 to 6.5.
Pectinases depolymerise pectin through hydrolysis, trans-elimination and deesterification reaction processes, breaking down the ester bond that holds together the carboxyl and methyl groups in pectin.
Endo-polygalacturonase progresses through a reaction along the following pathway: