J. D. Judah

The Biochemistry of Copper Deficiency. I. Enzymological Disturbances, Blood Chemistry and Excretion of Amino-Acids

The biochemistry of an uncomplicated deficiency of copper is studied. A moderate to advanced depletion of copper does not affect the activity or level of the following: liver-slice respiration, tricarboxylic acid cycle, fatty-acid oxidation, amino-acid oxidation, oxidative phosphorylation, anaerobic glycolysis, catalase, DPN-cytochrome c reductase, transmethylase, choline oxidase, isocitric dehydrogenase, succinic dehydrogenase, malic dehydrogenase, glutamic dehydrogenase, oxidation of glucose and pyruvate by brain mitochondria, urinary amino-acids, plasma protein, magnesium, calcium, sodium, potassium, or inorganic phosphate. Activities of cytochrome oxidase and succinoxidase are reduced at this stage of deficiency. The loss of succinoxidase activity is due to the depletion of cytochrome oxidase which is severe and progressive from a very early stage of deficiency. Haem α is almost completely absent from copper-deficient tissues, and it is suggested that this is the limiting component of the cytochrome oxidase system. Mitochondria from deficient rats are very susceptible to ‘ageing’. The ‘ageing’ effect is shown to be due to loss of and reversed by addition of the pyridine nucleotides, glutathione and manganese. The susceptibility to ‘ageing’ is thought to be secondary to an impaired synthesis of phospholipid. Extreme copper deficiency leads to a grave loss of the capacity of mitochondria to oxidize any substrate; this is almost certainly due both to the negligible activity of cytochrome oxidase and an acceleration oftheeffectof ‘ageing’. Isocitric dehydrogenase activity is increased and DPN-cytochrome c reductase decreased at this stage; the reasons are discussed.

The biochemistry of copper deficiency - II. Synthetic processes

The biochemistry of copper deficiency is studied in order to gain some understanding of the metabolic disturbances which lead to demyelination of the central nervous system in disease. In the preceding paper we reported our investigation of the enzyme systems, blood chemistry and amino-acid excretion in copper-deficient rats, and in this paper extend the study to investigate the syntheses of phospholipid, long-chain fatty acids, ribose nucleic acid, protein and protohaem. Phospholipid synthesis is found to be depressed considerably in copper deficiency. This is due to a failure in the process of condensation of acyl CoA with α-glycerophosphate to form phosphatidic acids. The reasons are discussed. The syntheses of long-chain fatty acids and ribose nucleic acid are normal, whilst the synthesis of protein is inconstantly affected by copper deficiency. Protohaem synthesis is depressed by a degree which exactly parallels the anaemia. The conclusion is drawn that the anaemia is due to a decrease in haematopoiesis rather than an increased destruction of red cells. The possible interrelationships of the disturbances of phospholipid synthesis and cytochrome oxidase activity and the relevance of each to demyelination of the central nervous system are discussed.

Action of some phenothiazine derivatives on the respiratory chain

Abstract Several phenothiazine tranquillizers and their derivatives have been tested against the respiration of liver mitochondria. Two actions have been found: Competitive inhibition of cytochrome oxidase and inhibition of DPNH-cytochrome- c reductase. The latter is manifested only in phosphorylating systems. There is some correlation between the effect on DPNH-cytochrome- c reductase and tranquillizing ability. Thus, chlorpromazine inhibits 90 per cent at 2 × 10 −4 M, at which concentration its sulphoxide has no effect. However, anomalies occur: acetylpromazine has little effect, but is a potent tranquillizer, and conversely, the primary amine of chlorpromazine is a powerful inhibitor, but is not a good tranquillizer.