A GH family 28 endo-polygalacturonase from the brown-rot fungus Fomitopsis palustris: Purification, gene cloning, enzymatic characterization and effects of oxalate

Abstract Brown-rot fungi are the wood-decay basidiomycetes and have ability to break down plant cell wall carbohydrates. It has been suggested that degradation of pectin is important for the initial stages of brown rot. We purified an endo -polygalacturonase ( Fp PG28A) from the brown-rot fungus Fomitopsis palustris , analysis of the predicted amino acid sequence indicated that Fp PG28A belongs to GH family 28. The highest activity of purified Fp PG28A was observed at 60 °C in 50 mM sodium acetate buffer (pH 5.0); this activity was highly specific for polygalacturonic acid chains. However, calcium polygalacturonate gel was not degraded by Fp PG28A under those optimal conditions. We observed that calcium polygalacturonate gel was readily degraded by the enzyme in the oxalate buffer. Furthermore, the thermostability of Fp PG28A was elevated in oxalate buffer at pH 3.0. These results indicated that oxalate has an important role in the degradation of woody pectin by Fp PG28A.