A Role of the Putidaredoxin COOH-terminus in P-450cam (Cytochrome m) Hydroxylations*
AUTOR(ES)
Sligar, S. G.
RESUMO
Methylene hydroxylation by cytochrome P-450cam (cytochrome m) can be resolved into four distinct steps: substrate addition, mo → mos; reduction, mos → mrs; dioxygen addition, mrs → mO2rs; followed by a second putidaredoxin (Pseudomonas putida ferredoxin)-mediated reduction and product formation. The isolated ferrous oxy-substrate complex exhibits first-order decay kinetics with the relatively slow rate constant of k [unk] 0.01 sec-1, at 25°, without product release. Putidaredoxin addition accelerates the decomposition with second-order kinetics, k [unk] 51,000 M-1 sec-1, and initiation of product formation. Cytochrome m forms a complex with putidaredoxin with dissociation constant of KD = 3 μM. In the complete three-protein hydroxylase system, consisting of cytochrome m, putidaredoxin, and the reductase (a DPNH-specific flavo-protein), camphor hydroxylation occurs with a stoichiometry of 1 mole each of DPNH and O2 used per mole of product formed; the KM for putidaredoxin is about 4.2 μM.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=434294Documentos Relacionados
- camR, a negative regulator locus of the cytochrome P-450cam hydroxylase operon.
- Detergent-soluble HLA antigens contain a hydrophilic region at the COOH-terminus and a penultimate hydrophobic region.
- SPIN-STATE CHANGES IN CYTOCHROME P-450cam ON BINDING OF SPECIFIC SUBSTRATES
- Purification and characterization of a cam repressor (CamR) for the cytochrome P-450cam hydroxylase operon on the Pseudomonas putida CAM plasmid.
- Evidence for autoregulation of camR, which encodes a repressor for the cytochrome P-450cam hydroxylase operon on the Pseudomonas putida CAM plasmid.
