Deciphering the mode of action, structural and biochemical analysis of heparinase II/III (PsPL12a) a new member of family 12 polysaccharide lyase from Pseudopedobacter saltans

Abstract

Heparinases are widely used for production of clinically and therapeutically important bioactive oligosaccharides and in analyzing the polydisperse, heterogeneous, and complex structures of heparin/heparan sulfate. In the present study, the gene (1911 bp) encoding heparinase II/III of family 12 polysaccharide lyase (PsPL12a) from Pseudopedobacter saltans was cloned, expressed, and biochemically and functionally characterized. The purified enzyme PsPL12a of molecular size approximately 76 kDa exhibited maximum activity in the temperature range 45–50 °C and at pH 6.0. PsPL12a gave maximum activity at 1% (w/v) heparin under optimum conditions. The kinetic parameters, K m and Vmax, for PsPL12a were 4.6 ± 0.5 mg/ml and 70 ± 2 U/mg, respectively. Ten millimolars of each Mg2+ and Mn2+ ions enhanced PsPL12a activity by 80%, whereas Ni2+ inhibited by 75% and Co2+ by 10%, and EDTA completely inactivated the enzyme. Protein melting curve of PsPL12a gave a single peak at 55 °C and 10 mM Mg2+ ions and shifted the peak to 60 °C. The secondary structure analysis of PsPL12a by CD showed 65.12% α-helix, 11.84% β-strand, and 23.04% random coil. The degradation products of heparin by PsPL12a analyzed by ESI-MS spectra displayed peaks corresponding to heparin di-, tetra-, penta-, and hexa-saccharides revealing the endolytic mode of enzyme action. Heparinase II/III (PsPL12a) from P. saltans can be used for production of low molecular weight heparin oligosaccharides for their utilization as anticoagulants. This is the first report on heparinase cloned from P. saltans.