87
6.2 Biochemical Characteristics of Pectinases
6.2.1 Pectinases
Pectinase or pectinolytic enzyme is a heterogeneous group of enzymes which is
used in hydrolyzing the pectic substances. Pectinase is comprised of many groups
or types (Sharma et al. 2013; Garg et al. 2016; Kubra et al. 2018; Guo et al. 2019).
It is classified into three major groups which are pectinesterases, protopectinase,
and depolymerizing enzymes (Kashyap et al. 2001; Kubra et al. 2018). Furthermore,
pectinase group can be classified according to their preferred substrate (pectin, pectic acid, or oligo-D-galacturonate), the degradation mechanism (trans-elimination
or hydrolysis), and the type of cleavage (random terminal endo or exo) (FavelaTorres et al. 2006; Kubra et al. 2018). The major part of pectinases can be summarized in Table 6.1. Numerous studies were extensively done on the production of
pectinolytic enzymes for the effect of different carbon sources and strains (Said
et al. 1991; Channe and Sitewale 1995; Arotupin 2007; El-Enshasy et al. 2018; Guo
et al. 2019). Among all strains, Aspergillus niger is commonly used for the industrial production of pectolytic enzymes (Esawy et al. 2013; El-Enshasy et al. 2018;
Sandri and Moura da Silveira 2018; Abdullah et al. 2018). This fungus synthesizes
polygalacturonase, polymethylgalacturonase, pectin lyase, and pectinesterase.
According to Debing et al. (2006), polygalacturonase, pectinesterase, and pectin
lyse are contributing to the breakdown and modification of pectins from a wide
variety of plant materials including the citrus pectin.
6.2.1.1 Mode of Action of Pectinases
As explained by Hoondal et al. (2002), an enzyme that hydrolyzes the pectic substances is usually known as pectinases and is comprised of polygalacturonases, pectin esterases, pectin lyases, and pectate lyases depending on their mode of action
(Fig. 6.1). In view of this fact, this study focused on A. niger that synthesizes pectinolytic enzymes polymethylgalacturonases (PMG) and polygalacturonases (PG);
thus, the mode of action of pectinase towards the pectic substance is called as depolymerization (Pedrolli et al. 2009). By referring to Table 6.1, the mechanism of
hydrolysis takes part for the PMG and PG since hydrolysis is known as the chemical
reaction in which water reacts with a compound to produce other compounds or
process that involves the splitting of a bond and the addition of the hydrogen cation
and the hydroxide anion from the water. In mechanism, the PMG and PG react
towards the pectic substrates and break the glycosidic linkage. The action of the
enzyme may be varied depending on its pattern, whether it is random or terminal,
and can be defined as endo or exo (Pedrolli et al. 2009).
6 Fungal Pectinases: Production and Applications in Food Industries
6.2 Biochemical Characteristics of Pectinases
6.2.1 Pectinases
Pectinase or pectinolytic enzyme is a heterogeneous group of enzymes which is
used in hydrolyzing the pectic substances. Pectinase is comprised of many groups
or types (Sharma et al. 2013; Garg et al. 2016; Kubra et al. 2018; Guo et al. 2019).
It is classified into three major groups which are pectinesterases, protopectinase,
and depolymerizing enzymes (Kashyap et al. 2001; Kubra et al. 2018). Furthermore,
pectinase group can be classified according to their preferred substrate (pectin, pectic acid, or oligo-D-galacturonate), the degradation mechanism (trans-elimination
or hydrolysis), and the type of cleavage (random terminal endo or exo) (FavelaTorres et al. 2006; Kubra et al. 2018). The major part of pectinases can be summarized in Table 6.1. Numerous studies were extensively done on the production of
pectinolytic enzymes for the effect of different carbon sources and strains (Said
et al. 1991; Channe and Sitewale 1995; Arotupin 2007; El-Enshasy et al. 2018; Guo
et al. 2019). Among all strains, Aspergillus niger is commonly used for the industrial production of pectolytic enzymes (Esawy et al. 2013; El-Enshasy et al. 2018;
Sandri and Moura da Silveira 2018; Abdullah et al. 2018). This fungus synthesizes
polygalacturonase, polymethylgalacturonase, pectin lyase, and pectinesterase.
According to Debing et al. (2006), polygalacturonase, pectinesterase, and pectin
lyse are contributing to the breakdown and modification of pectins from a wide
variety of plant materials including the citrus pectin.
6.2.1.1 Mode of Action of Pectinases
As explained by Hoondal et al. (2002), an enzyme that hydrolyzes the pectic substances is usually known as pectinases and is comprised of polygalacturonases, pectin esterases, pectin lyases, and pectate lyases depending on their mode of action
(Fig. 6.1). In view of this fact, this study focused on A. niger that synthesizes pectinolytic enzymes polymethylgalacturonases (PMG) and polygalacturonases (PG);
thus, the mode of action of pectinase towards the pectic substance is called as depolymerization (Pedrolli et al. 2009). By referring to Table 6.1, the mechanism of
hydrolysis takes part for the PMG and PG since hydrolysis is known as the chemical
reaction in which water reacts with a compound to produce other compounds or
process that involves the splitting of a bond and the addition of the hydrogen cation
and the hydroxide anion from the water. In mechanism, the PMG and PG react
towards the pectic substrates and break the glycosidic linkage. The action of the
enzyme may be varied depending on its pattern, whether it is random or terminal,
and can be defined as endo or exo (Pedrolli et al. 2009).
6 Fungal Pectinases: Production and Applications in Food Industries