Purification and properties of a β-1,6-glucanase from Streptomyces sp. EF-14, an actinomycete antagonistic to Phytophthora spp.

Abstract

Extracellular enzymes with glucanase activities are an important component of actinomycete-fungus antagonism. Streptomyces sp. EF-14 has been previously identified as one of the most potent antagonists of Phytophthora spp. A beta-1,6-glucanase (EC 3.2.1.75; glucan endo-1,6-beta-glucosidase) was purified by four chromatographic steps from the culture supernatant of strain EF-14 grown on a medium with lyophilized cells of Candida utilis as main nutrient source. The glucanase level in this medium followed a characteristic pattern in which the rise of beta-1,6-glucanase activity always preceded that of beta-1,3-glucanase. The molecular mass of the enzyme was estimated to be 65 kDa and the pI approximately 5.5. It hydrolyzed pustulan by an endo-mechanism generating gentiobiose and glucose as final products. Laminarin was not hydrolyzed indicating that the enzyme does not recognize beta-1,6-links flanked by beta-1,3-links. No significant clearing of yeast cell walls in liquid suspensions or in agar plates was observed indicating that this beta-1,6-glucanase is a non-lytic enzyme. This is the first beta-1,6-glucanase characterized from an actinomycete.

Biochemical Characterization of Recombinant Thermostable Cohnella sp. A01 β-Glucanase

“…Laminarin is the best substrate for bg16M activity, and it had a relative activity on pustulan. Other enzymes had activity have a ctivity on both substrates have also been reported[ 26 ]. T. harzianum bg16M enzyme had no effects on the glucans extracted from S .…”

“…The bg16M in Trichoderma harzianum and Streptomyces sp. EF-14 and Penicillium multicolor had molecular weights about 43 and 51 kDa, respectively[ 13 , 26 , 27 ].…”

“…The bg16M had no activity on laminarin, which may be due to inability of the enzyme to recognize β-1,6 bond near the 1, 3-glycosidic bonds. In other words, these enzymes require the substrates that are all β-1,6-glycosidic bonds with no gap between[ 26 ]. Table 2 shows heterogenesity of some bg16M enzymes.…”

“…had optimum activity at pH 5.5. Enzyme from P. multicolor showed optimal activity at pH 4; nevertheless, no bg16M was observed with the optimal activity in the alkaline conditions[ 26 , 27 , 30 ].…”

“…The optimum temperature of the enzyme extracted from Streptomyces sp. has been reported to be at 55 °C[ 26 ], in P. multicolor is 50 °C[ 27 ], and in Acremonium sp., the optimal activity of IMI 383068 was observed at 40 °C in pH 5 and at 50 °C in pH 5.6[ 33 ].…”