Different molecular forms of D-ribulose-1,5-bisphosphate carboxylase from Rhodopseudomonas sphaeroides.
Ribulose-1,5-bisphosphate (Rbu-P2) carboxylase isolated from Rhodopseudomonas sphaeroides 2.4.1.Ga was separated into two different forms by DEAE-cellulose column chromatography. Both forms, designated Peak I and Peak II have been purified to homogeneity by the criterion of polyacrylamide disc-gel electrophoresis. The Peak I carboxylase has a molecular weight of 550,000, while the Peak II carboxylase is a smaller protein having a molecular weight of approximately 360,000. Sodium dodecyl sulfate electrophoresis revealed a large subunit for both enzymes which migrates similarly to the large subunit of spinach Rbu-P2 carboxylase. The Peak I enzyme also exhibited a small subunit having a molecular weight of 11,000. No evidence for a smaller polypeptide was found associated with the Peak II enzyme. Antisera prepared against the Peak I enzyme inhibited Peak I enzymatic activity, but had no effect on the activity of the Peak II enzyme. The two enzymes exhibited marked differences in catalytic properties. The Peak I enzyme exhibits optimal activity at pH 8.0 and is inhibited by low concentrations of 6-phosphogluconate, while the Peak II enzyme has a pH optimum of 7.2 and is relatively insensitive to 6-phosphogluconate.
D002262:Carboxy-Lyases / Q000378:metabolism; D005942:Gluconates / Q000494:pharmacology; D006863:Hydrogen-Ion Concentration; D007118:Immunoassay; D005779:Immunodiffusion; D007527:Isoenzymes / Q000302:isolation & purification / Q000378:metabolism; D007700:Kinetics; D008970:Molecular Weight; D012242:Rhodobacter sphaeroides / Q000201:enzymology*; D012273:Ribulose-Bisphosphate Carboxylase / Q000302:isolation & purification / Q000378:metabolism; D013403:Sugar Phosphates / Q000494:pharmacology
D005942:Gluconates; D007527:Isoenzymes; D013403:Sugar Phosphates; D002262:Carboxy-Lyases; D012273:Ribulose-Bisphosphate Carboxylase