DEFECTS IN THE MITOCHONDRIAL ENERGY-METABOLISM OUTSIDE THE RESPIRATORY-CHAIN AND THE PYRUVATE-DEHYDROGENASE COMPLEX

Disturbances in substrate oxidations in muscle mitochondria from patie nts with a suspicion of a mitochondrial myopathy may arise from a defi ciency of one or more of the complexes of the respiratory chain or of the pyruvate dehydrogenase complex. However, we found no clear-cut def ect in a substantial part of such patients. In this report we discuss some of the other possibilities which could account for the disturbed substrate oxidation rates. Special attention will be paid to defects w hich are localized outside the respiratory chain, such as defects in p ost-respiratory chain enzymes, defects in transport mechanisms of the mitochondrial inner or outer membrane, deficiency of cofactors and def iciency of heat-shock protein.