Pectic, classification

Classification of Depolymerizing Pectic Enzymes According to Neukom5... 

Investigations of pectic enzymes conducted during the past few years have shown that the classification system due to Neukom5 is no longer adequate. Thus, the hypothetical enzymes degrading highly... 

The classification of pectic enzymes in general, their occurrence in higher plants and micro-organisms and the properties of pectic enzymes from some plants and food grade micro-organisms are described with special emphasis on their substrate specificity. Their technological roles and applications, also in combination with (hemi-)cellulases, in a variety of processes are discussed. Evidence is presented for the existence of a new type of pectic enzyme which acts specifically in the hairy regions of pectic substances. 

Much of the confusion in pectic enzyme terminology was clarified by Demain and PhaflF in 1957 12) and Deuel and Stutz in 1958 11). Their classification of depolymerases was based on the substrate attacked (pectin m. non-esterified polygalacturonic acid), the mode of attack (random or endo attack vs. terminal or exo attack), and the optimal pH for enzyme activity. However it was assumed that hydrolysis was the... 

A recent classification (1 ) describes the pectic polysaccharides as those polymers found in covalent association with galactu-ronosyl-containing polysaccharides. The hemicelluloses are those carbohydrate polymers which are noncovalently associated with cellulose. Diverse categories of pectic polysaccharides occur not only among plant sources, but among tissues in a given source. 

A more recent, clearly preferable classification (Brillouet, 1987 Brillouet et al, 1989) simply divides soluble polysaccharides in must into neutral pectic substances and acid pectic substances, depending on whether or not the molecules contain... 

Classification of the pectic substances is an area that grabbed much attention of the polymer biochemistry. Pectic polysaccharides are in fact, recognized in several forms and accordingly, they have been classified into distinct groups. The American Chemical Society classified pectic substances into fom main groups as follows (Kertesz, 1951). 

However, it needs mentioning in this context that classification and nomenclature of pectic substances in consideration to their chemical solrrbility in differertt solverrls has also been emphasized. In this context, pectic substances are classified broadly irrto the following groups (Bamier and Thibault, 1982). 

Pectin was discovered by Braconnot in 1825, but not until 1917 was the major building unit of all pectins, D-galacturonic acid, discovered by Ehrlich and Suarez . The presence of methyl ester groups in pectins was discovered by Von Fellenberg in 1913. Yet it was only in the early 1930 s that any degree of unanimity could be attained in the classification and nomenclature of pectic substances. A major factor in this development was the then increasing and now general acceptance of the macromolecular concept for pectins , a subject discussed below. 

The original classification of wall polysaccharides can be related to the modem terminology, as mild acid preferentially extracts the pectic polysaccharides, while subsequent extraction with alkali preferentially solubilizes the hemicelluloses. Therefore, in this review, discussion of the non-eellulosic cell wall polysaccharides will be found under the general headings of the pectic polysaccharides and the hemicelluloses. Cellulose as well as the non-polysaccharide components of primary cell walls will also be considered. 

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