Biochemical and Pharmacokinetic Properties of PEGylated Cystathionine γ-Lyase from Aspergillus carneus KF723837

Cystathionine γ-lyase (CGL) was purified to its electrophoretic homogeneity from Aspergillus carneus by various chromatographic approaches. The purified enzyme has four identical subunits of 52 kDa based on SDS and native PAGE analyses. To improve its structural stability, purified CGL was modified by covalent binding to polyethylene glycol moieties. The specific activity of free-CGL and PEG-CGL was 59.71 and 48.71 U/mg, respectively, with a PEGylation yield of 81.5 and 70.7% modification of surface ε-amino groups. Free- and modified CGL have the same pattern of pH stability (8.0-9.0). At 50°C, the thermal stability [half-life time (T 1/2 )] of PEG-CGL was increased by 40% in comparison to free-CGL. The activity of CGL was completely inhibited by hydroxylamine and Hg +2 , with no effect by EDTA. Free-CGL (0.04 m M -1 s -1 ) and PEG-CGL (0.03 m M -1 s -1 ) have a similar catalytic efficiency to L -cystathionine as a substrate. The inhibition constant values of propargylglycine were 0.31 and 0.52 µ M for the free- and PEG-CGL, respectively. By in vitro proteolysis, PEG-CGL retains >50% of its initial activity compared to