Functional characterization of two human sulphotransferase cDNAs that encode monoamine- and phenol-sulphating forms of phenol sulphotransferase : substrate kinetics, thermal-stability and inhibitor-sensitivity studies

摘要: The present paper describes the functional characterization of two human aryl sulphotransferase (HAST) cDNAs, HAST1 and HAST3, previously isolated by us from liver brain, respectively [Zhu, Veronese, Sansom, McManus (1993) Biochem. Biophys. Res. Commun. 192, 671-676; Zhu, Bernard, Sansom 195, 120-127]. These appear to encode major forms phenol (PST) characterized in a number tissue cytosols, these being phenolsulphating (P-PST) monoamine-sulphating (M-PST) sulphotransferase. HAST3 cDNAs were functionally expressed COS-7 cells kinetically using model substrates for P-PST M-PST, p-nitrophenol dopamine (3,4-dihydroxyphenethylamine) respectively. COS-expressed was shown be enzymatically active sulphating with high affinity (Km 0.6 microM), whereas preferred substrate 9.7 microM). could also sulphate dopamine, as p-nitrophenol, but Km reactions at least orders magnitude greater than substrates. displayed inhibition profiles ST inhibitor 2,6-dichloro-4-nitrophenol (DCNP), identical cytosolic M-PST activities Thermal-stability studies enzymes showed that considerably more thermostable (TS) which is consistent termed TS PST thermolabile (TL) PST. Western immunoblot analyses proteins an antibody generated bacterially rat aryl/phenol migrated single different electrophoretic mobilities (32 versus 34 kDa). This differences observed variety tissues reported other workers. report on provides important information structural well relationships PSTs, vast array exogenous endogenous compounds.