Common amino acid domain among endopolygalacturonases of ascomycete fungi

Abstract

The endopolygalacturonase (EC 3.2.1.15) enzymes produced in vitro by three ascomycete fungi, Aspergillus niger, Sckerotinia scierotiorum, and Colletotrichum lindemuthianum were studied by using thin-layer isoelectric focusing and activity stain overlay techniques. The polygalacturonases from A. niger and S. sclerotiorum consisted of numerous isoforms, whereas the endopolygalacturonase from C. lindemuthianum consisted of a single protein species. The most abundant endopolygalacturonase isoform produced by each of these organisms was purified and characterized. Biochemical parameters, including molecular weight, isoelectric point, kinetic parameters, temperature and pH optima, and thermal stability, were determined. Considerable differences in physical and chemical properties were demonstrated among these fungal polygalacturonases. Antibodies raised against individual proteins exhibited little cross-reaction, suggesting that these enzymes differ structurally as well as biochemically. In contrast, the analysis of the N-terminal amino acid sequences of the three proteins showed extensive homology, particularly in a region labeled domain 1 in which 84% of the amino acids were conserved.

Purification and Characterization of Extracellular Pectinolytic Enzymes Produced by Sclerotinia sclerotiorum

“…This indicates that the exoPG is likely to be a single polypeptide protein, while the native exoPMG is composed of two identical subunits. The Mrs of these exoenzymes are higher than those of the endoPGs which are secreted by this fungus and which are in the range of 28,000 to 43,000 (18,24).…”

“…Decomposition of plant cell walls during tissue invasion and pathogenesis is a characteristic feature of numerous plant diseases caused by phytopathogenic fungi (9,18). These fungi are able to produce a large array of cell walldegrading enzymes, both in culture and in diseased plant tissues.…”

“…Among the phytopathogenic fungi, Sclerotinia sclerotiorum is a ubiquitous fungus that is able to infect a wide range of plants and that secretes a complete set of enzymes to macerate healthy plant tissues (16,22,31). Although endo-,B-1,4-galactanase, a-L-arabinofuranosidase, and endopolygalacturonases (endoPGs) from this fungus have been investigated previously (2,6,13,18,24), extracellular pectinolytic enzymes have not yet been characterized. Studies of microorganisms able to grow on a cell wall polymer raise the question of how these microbes can recognize the substrate in their environment even though large molecules cannot penetrate the cell wall and membrane.…”

The ability of Gremmeniella abietina to hydrolyze polygalacturonic acid

“…At pH 7.5 the activity was completely undetectable and at 8.5 minimal. The reported polygalacturonase enzyme activity oi Aspergillus nidulans was also highest at or below pH 4 (DEAN and TIMBERLAKE 1989) and that of Aspergillus niger and Sclerotinia sclerotiorum at pH 4.2 (KEON and WAKSMAN 1990). BAILEY and PESSA (1990) found that the pH optimum of the A. niger polygalacturonase was between pH 4.5-5.0.…”

The polygalacturonases of Aspergillus niger are encoded by a family of diverged genes

“…Also, a single deletion of two amino acids is observed with respect to the sequences of the three other fungal polygalacturonases (data not shown). Alignment of the N-terminal amino acid sequences of these polygalacturonases with those of the major polygalacturonases of Colletotrichum lindeniuthiunum and Sclerotiniu sclerotiorunz [30] is shown in Fig. 5.…”