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Extensive Classification of Pectinases⁽¹⁾

The Pectinolytic Enzymes may be divided in three broader groups as follows:

(I) Protopectinases

They degrade the insoluble protopectin and give rise to highly polymerized soluble pectin. The enzyme that catalyzes the solubilization of protopectin was originally named protopectinase by Briton et al. Pectinosinase is also synonymous with protopectinase (PPase). Protopectinase catalyzes the following reaction:

                                                                    Protopectinase 

                          Protopectin (Insoluble) + H₂0           à             Pectin (soluble)

PPases are classified into two types, on the basis of their reaction mechanism. A-type PPases react with the inner site, i.e. the polygalacturonic acid region of protopectin, whereas B-type PPases react on the outer site, i.e. on the polysaccharide chains that may connect the polygalacturonic acid chain and cell wall constituents. A-type PPase are found in the culture filtrates of yeast and yeast-like fungi. They have been isolated from Kluyveromyces fragilis IFO 0288, Galactomyces reesei L. and Trichosporon penicillatum SNO 3 and are referred to as PPase-F, -L and -S, respectively. B-type PPases have been reported in Bacillus subtilis IFO 12113, B. subtilis IFO 3134 and Trametes sp., and are referred to as PPase- B, -C and -T, respectively. B-type PPases have also been found in the culture filtrate of a wide range of Bacillus sp.

All three A-type PPases are similar in biological properties and have similar molecular weight of 30 kDa. PPase-F is an acidic protein, and PPase-L and -S are basic proteins. The enzymes have pectin-releasing effects on protopectin from various origins. The enzymes catalyze the hydrolysis of polygalacturonic acid; they decrease the viscosity, slightly increasing the reducing value of the reaction medium containing polygalacturonic acid. PPase-B, -C and -T have molecular weights of 45, 30, and55 kDa, respectively. PPase-B and -C have an isoelectricpoint (pI) of around 9.0 whereas PPase-T has a pI of 8.1. PPase-B, -C and -T act on protopectin from various citrus fruit peels and other plant tissues, releasing pectin.

(II) Esterases

They catalyze the de-esterification of pectin by the removal of methoxy esters.

(III) Depolymerases

They catalyze the hydrolytic cleavage of the a-(1®4) -glycosidic bonds in the D-galacturonic acid moieties of the pectic substances.

Alternative names of Enzymes:

EC: 3.1.1.11:

Accepted Name: Pectinesterase

Other Names: Pectin demethoxylase; pectin methoxylase; pectin methylesterase; pectase; pectin methyl esterase; pectinoesterase.

Systematic name: Pectin pectylhydrolase

EC 3.2.1.15:

Accepted Name: Polygalacturonase

Other names: Pectin depolymerase; pectinase; endopolygalacturonase; pectolase; pectin hydrolase; pectin polygalacturonase; endo-polygalacturonase; poly-α-1,4-galacturonide glycanohydrolase; endogalacturonase; endo-D-galacturonase

Systematic name: Poly(1,4-α-D-galacturonide) glycanohydrolase

EC 3.2.1.67:

Accepted name: Galacturan 1,4-α-galacturonidase

Other names: Exopolygalacturonase; poly(galacturonate) hydrolase; exo-D-galacturonase; exo-D-galacturonanase; exopoly-D-galacturonase

Systematic name: Poly(1,4-α-D-galacturonide) galacturonohydrolase

EC 3.2.1.82:

Accepted name: Exo-poly-α-galacturonosidase

Other names: Exopolygalacturonosidase; exopolygalacturanosidase

EC 4.2.2.2:

Accepted name: Pectate lyase

Other names: Polygalacturonic transeliminase; pectic acid transeliminase; polygalacturonate lyase; endopectin methyltranseliminase; pectate transeliminase; endogalacturonate transeliminase; pectic acid lyase; pectic lyase; α-1,4-D-endopolygalacturonic acid lyase; PGA lyase; PPase-N; endo-α-1,4-polygalacturonic acid lyase; polygalacturonic acid lyase; pectin trans-eliminase; Polygalacturonic acid trans-eliminase

Systematic name: (14)-α-D-galacturonan lyase

EC 4.2.2.9:

Accepted name: Pectate disaccharide-lyase

Other names: Pectate exo-lyase; exopectic acid transeliminase; exopectate lyase; exopolygalacturonic acid-trans-eliminase; PATE; exo-PATE; exo-PGL

Systematic name: (14)-α-D-galacturonan reducing-end-disaccharide-lyase

EC 4.2.2.6:

Accepted name: Oligogalacturonide lyase

Other names: Oligogalacturonate lyase; unsaturated oligogalacturonate transeliminase; OGTE

Systematic name: Oligogalacturonide lyase

EC 4.2.2.10:

Accepted name: Pectin lyase

Other names: Pectin trans-eliminase; endo-pectin lyase; polymethylgalacturonic transeliminase; pectin methyltranseliminase; pectolyase; PL; PNL; PMGL

Systematic name: (14)-6-O-methyl-α-D-galacturonan lyase