Gene/Protein
Disease
Symptom
Drug
Enzyme
Compound
Pivot Concepts:
Gene/Protein
Disease
Symptom
Drug
Enzyme
Compound
Target Concepts:
Gene/Protein
Disease
Symptom
Drug
Enzyme
Compound
Query: EC:2.5.1.18 (
glutathione S-transferase
)
22,582
document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)
Rat liver phosphoribosylpyrophosphate (PRPP) synthetase exists as complex aggregates composed of 34-kDa catalytic subunits (PRS I and PRS II) and homologous 39- and 41-kDa proteins termed PRPP synthetase-associated proteins (PAPs). While a negative regulatory role was indicated for PAPs, the physiological function of PAPs is less well understood. We attempted to prepare recombinant 39-kDa PAP (
PAP39
) and to reconstitute the enzyme complex. Free
PAP39
was poorly expressed in Escherichia coli, while expression of protein fused with
glutathione S-transferase
was successful. The purified fusion protein had no PRPP synthetase activity, and bound to dissociated PRS I and PRS II, with a similar affinity. A free form of
PAP39
prepared from the fusion protein formed insoluble aggregates. The enzyme complex was then partially reconstituted in situ by coexpression of
PAP39
with PRS I or PRS II in E. coli cells. This coexpression led to formation of soluble complexes of various compositions, depending on the conditions. When the relative amount of
PAP39
was higher, specific catalytic activities, in terms of the amount of the catalytic subunit, were lowered.
PAP39
complexed with PRS I was more readily degraded by proteolysis than seen with PRS II, in vivo and in vitro. These results provide additional, strong evidence for that
PAP39
has no catalytic activity in the enzyme complex, but does exert inhibitory effects in an amount-dependent manner, and that composition of the enzyme complex varies, depending on the relative abundance of components present at the site of aggregate formation.
...
PMID:Partial reconstitution of mammalian phosphoribosylpyrophosphate synthetase in Escherichia coli cells. Coexpression of catalytic subunits with the 39-kDa associated protein leads to formation of soluble multimeric complexes of various compositions. 936 67
