The objective of the proposed studies is to characterize the function, regulation and consequences of the inhibition of key mitochondrial enzymes in order to understand the effect of these enzymes and their inhibition on the metabolism of the cell and their involvement in the toxicology of environmental chemicals. As well as providing basic information on the nature and properties of the enzymes to be studied, the health-related aims of the proposed experiments are: (1) to elucidate factors affecting the transfer of fatty acids which are an important fuel source, especially in liver and heart. A new view of the role of peroxisomal carnitine palmitoyltransferase in fatty acid metabolism will also be investigated; (2) to investigate the intracellular biochemical events which lead to the onset of Parkinson's disease, a sequence which involves monamine oxidase, an energy-dependent mitochondrial uptake process, and inhibition of the respiratory enzyme, NADH-Q oxidoreductase; (3) to identify potential environmental toxins which may be responsible for the onset of Parkinson's disease using the relatively simple in vitro systems listed above; (4) to survey these same toxins as substrates and inhibitors of monoamine oxidase, because inhibition of either the A or B forms (which have different specificities) can seriously disturb amine metabolism both in the brain and in peripheral tissues. Biochemically, the mechanisms, function and structure of the enzyme systems involved will be studied in intact mitochondria from normal and diseased tissues, in membrane fragments and isolated enzymes, using inhibitors and alternate substrates to examine regulation and malfunction. Studies on monoamine oxidase will continue using steady-state and pre-steady state kinetics to study the mechanism(s) of the two forms of the enzyme and their specificities with pyridine derivatives to correlate with or predict in vivo toxicity of such compounds. The toxicity of pyridinium compounds to mitochondrial respiration, which leads to cell death, will be explored. Their chemical versatility presents a unique opportunity to study the Q-binding site of NADH-Q oxidoreductase and to characterize the mitochondrial cation accumulation system, both of which are implicated in the onset of acute Parkinsonism.
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