Molecular Cloning and Characterization of a Novel Exo-β-1,3-Galactanase from Penicillium oxalicum sp. 68

Arabinogalactans have diverse biological properties and can be used as pharmaceutical agents. Most arabinogalactans are composed of beta-(1 -> 3)-galactan, so it is particularly important to identify beta-1,3-galactanases that can selectively degrade them. In this study, a novel exo-beta-1,3-galactanase, named PoGal3, was screened from Penicillium oxalicum sp. 68, and hetero-expressed in P. pastoris GS115 as a soluble protein. PoGal3 belongs to glycoside hydrolase family 43 (GH43) and has a 1,356-bp gene length that encodes 451 amino acids residues. To study the enzymatic properties and substrate selectivity of PoGal3, beta-1,3-galactan (AG-P-I) from larch wood arabinogalactan (LWAG) was prepared and characterized by HPLC and NMR. Using AG-P-I as substrate, purified PoGal3 exhibited an optimal pH of 5.0 and temperature of 40 degrees C. We also discovered that Zn(2+)had the strongest promoting effect on enzyme activity, increasing it by 28.6%. Substrate specificity suggests that PoGal3 functions as an exo-beta-1,3-galactanase, with its greatest catalytic activity observed on AG-P-I. Hydrolytic products of AG-P-I are mainly composed of galactose and beta-1,6-galactobiose. In addition, PoGal3 can catalyze hydrolysis of LWAG to produce galacto-oligomers. PoGal3 is the first enzyme identified as an exo-beta-1,3-galactanase that can be used in building glycan blocks of crucial glycoconjugates to assess their biological functions.

Automated summary

In this study, a novel exo-beta-1,3-galactanase named PoGal3 was identified and characterized. PoGal3 showed optimal activity at pH 5.0 and 40°C with beta-1,3-galactan as the preferred substrate. It also exhibited enhanced activity in the presence of Zn(2+). This enzyme has potential applications in the construction of glycan blocks for studying biological functions.