Interaction of pyridoxal phosphate analogues with apoenzymes of gamma-cystathionase and serine sulphhydrase

Comparative studies have been done of the interactions of some coenzyme analogues with the apoenzymes of γ-cystathionase (EC 4.2.1.15) from rat liver and serine sulphhydratase (EC 4.2.1.22) from chicken liver — pyridoxal-phosphate-dependent enzymes catalysing reactions of H₂S release from L-cystein $\text{via}$ α,β-elimination and β-substitution, respectively. It was found that minor modifications (substitutions) in the structure of pyridoxal-5′-phosphate (pyridoxal-P; PLP) result in marked lowering of affinity of the analogues for the apoenzymes. Considerable differences were observed between the various apoenzymes in regard to the mode of their interaction with the pyridoxal-P analogues used.