This proposal represetns a continuation of our efforts to isolate, purify, and characterize isozymes of cytochrome P-450 which are endogenous to liver microsomes of the untreated animal. Such procedures wil utilize sequential steps of hydrophobic, cationic and anionic column chromatography. Two forms of cytochrome P-450 have already been characterized and three more have reached a stage of purity whereby separation procedures will gear up for sufficient amounts for characterization. Attempts will be made to discern the role of these isozymes in maintaining the homeostasis of the animal; compounds of endogenous origin, e.g., testosterone, progesterone, estradiol, cholesterol and fatty acids will be examined as substrates. The type I binding site, the region where substrates bind, will be studied to determine its dimension. Substrates of increasing size will be used until restriction of carbon monoxide binding is observed. Pressure studies for volume change mesurements will also be performed. The amino acid composition of the type I site will be determined using amino acid reagents and measuring their affect on substrate binding and protection from reagents by substrates. The mechanism of action of the P-450 system will be studied in steps, assessing the influence of spin state of the ferric cytochrome and reductase binding on the kinetics of reduction. The oxygen sensitivity of the reaction will also be measured. These spectral studies will be backed by development of thermodynamic models and mathematical modeling. The roles of cytochrome b5 in P-450 monooxygenation will also be studied and attempts will be made to explain the mechanism of NADH synergism. In addition, differences in influence of cytochrome b5 on the NADPH-dependent metabolism of different substrates will be examined to determine whether metabolite patterns are altered. Attemps will be made to learn the reason for observed differences.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
5R01GM026114-10
Application #
3273606
Study Section
Pharmacology A Study Section (PHRA)
Project Start
1978-06-01
Project End
1988-05-31
Budget Start
1987-06-01
Budget End
1988-05-31
Support Year
10
Fiscal Year
1987
Total Cost
Indirect Cost
Name
University of Connecticut
Department
Type
School of Medicine & Dentistry
DUNS #
City
Farmington
State
CT
Country
United States
Zip Code
06030
Jansson, I; Mole, J E; Schenkman, J B (1995) The isolation and comparison of multiple forms of CYP2B from untreated and phenobarbital-treated rabbit liver microsomes. Arch Biochem Biophys 316:275-84
Voznesensky, A I; Schenkman, J B; Pernecky, S J et al. (1994) The NH2-terminal region of rabbit CYP2E1 is not essential for interaction with NADPH-cytochrome P450 reductase. Biochem Biophys Res Commun 203:156-61
Voznesensky, A I; Schenkman, J B (1994) Quantitative analyses of electrostatic interactions between NADPH-cytochrome P450 reductase and cytochrome P450 enzymes. J Biol Chem 269:15724-31
Schenkman, J B; Voznesensky, A I; Jansson, I (1994) Influence of ionic strength on the P450 monooxygenase reaction and role of cytochrome b5 in the process. Arch Biochem Biophys 314:234-41
Richardson, T H; Schenkman, J B; Turcan, R et al. (1992) Molecular cloning of a cDNA for rat diabetes-inducible cytochrome P450RLM6: hormonal regulation and similarity to the cytochrome P4502E1 gene. Xenobiotica 22:621-31
Voznesensky, A I; Schenkman, J B (1992) The cytochrome P450 2B4-NADPH cytochrome P450 reductase electron transfer complex is not formed by charge-pairing. J Biol Chem 267:14669-76
Voznesensky, A I; Schenkman, J B (1992) Inhibition of cytochrome-P450 reductase by polyols has an electrostatic nature. Eur J Biochem 210:741-6
Cammer, W; Downing, M; Clarke, W et al. (1991) Immunocytochemical staining of the RLM6 form of cytochrome P-450 in oligodendrocytes and myelin of rat brain. J Histochem Cytochem 39:1089-94
Schenkman, J B (1991) Induction of diabetes and evaluation of diabetic state on P450 expression. Methods Enzymol 206:325-31
Sinclair, J F; McCaffrey, J; Sinclair, P R et al. (1991) Ethanol increases cytochromes P450IIE, IIB1/2, and IIIA in cultured rat hepatocytes. Arch Biochem Biophys 284:360-5

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