Boyd L. O'Dell

A critical physiological role of zinc in the structure and function of biomembranes

Abstract Of the large number of recognized zinc metalloenzymes, the activities of only a few are significantly decreased in severely zinc deficient animals. On the other hand, physiological pathology is manifested rapidly after dietary zinc deprivation. This shows that zinc exerts physiological and biochemical roles other than as a component of the known zinc metalloenzymes. The research results reviewed here suggest that zinc plays an important role in the maintenance of membrane structure and function.

Connective tissue defect in the chick resulting from copper deficiency.

Summary Chicks reared for 4 weeks on a modified non-fat milk diet deficient in copper developed mild anemia, leg weakness, bone deformities and a high incidence of subcutaneous hemorrhage. Mortality amounted to 23% and most deaths resulted from internal hemorrhage associated with rupture of major vessels. Histologic studies suggest a derangement of connective tissue metabolism with the major defect in elastic tissue.

Connective tissue amine oxidase II. Purification and partial characterization of lysyl oxidase from chick aorta

Abstract An amine oxidase, lysyl oxidase, which catalyzes the oxidation of peptidyl lysine has been isolated from immature chicken aortas. Although insoluble in salt buffers, the enzyme was extracted from the tissue with 4 M urea. A combination of DEAE-cellulose and affinity chromatography was used to purify the enzyme to a level 2400 times the concentration found in the tissue. The enzyme catalyzed the formation of tritiated water from [6- 3 H]lysine-labeled proteins produced by embryonic aortas grown in organ culture. Soluble protein in the culture medium as well as protein in the insoluble tissue served as substrate(s). Saturation kinetics were observed with both sources of substrate. The enzyme activity was inhibited by β-aminopropionitrile, dithiothreitol and reagents that react with carbonyl groups. Sodium dodecylsulfate acrylamide gel electrophoresis of the purified enzyme revealed two major protein bands which had estimated molecular weights of 59 000 and 61 000. At this stage of purity the enzyme contained 0.14% copper. Mild acid treatment resulted in the loss of enzyme activity and dialysis of the partially inactivated enzyme against copper restored full activity. It is concluded that aortic lysyl oxidase is a copper metalloenzyme.

Effects of copper and zinc status of rats on erythrocyte stability and superoxide dismutase activity.

Summary Erythrocytes from copper deficient rats, which had normal plasma zinc but low plasma copper (high Zn:Cu), were more stable to osmotic stress than those from controls. Erythrocytes from zinc deficient rats, which had low plasma zinc and high plasma copper (low Zn:Cu), were more fragile than those from controls. Addition of Cu2+ and Zn2+ to normal red cells in vitro to provide a low Zn:Cu ratio increased hemolysis and peroxidation. In general erythrocyte membranes are sensitive to the concentrations of extracellular Cu and Zn. The effects are inversely related, zinc exerting a stabilizing and copper a labilizing effect. Ceruloplasmin levels increased in zinc deficiency but RBC superoxide dismutase activity was unaffected. SOD activity is suggested as a clinical index of tissue copper status.

Biochemistry of Copper

Copper, as a component of numerous cuproenzymes, plays a vital role in many physiologic functions in man and animals. From the stand-point of human health there are at least three functional areas of prime importance. Copper is involved in the development and maintenance of cardiovascular and skeletal integrity, central nervous system structure and function, and erythropoietic function including iron metabolism. Although there is no evidence for widespread copper deficiency in the human population, it does occur, owing to genetic defects and other precipitating factors. A clear understanding of the functions of copper and its mechanisms of action could prove highly beneficial in the solution of present and unforeseen problems in medicine.

Mineral interactions relevant to nutrient requirements.

The negative interaction of metal ions is one of the major dietary factors that causes low bioavailability of these nutrients. Interactions of nutritional significance include sodium-potassium, calcium-magnesium, manganese-iron, iron-copper, and zinc-copper. These interactions reach potential importance when the first metal of each pair listed above is in excess and the other is at the lower limit of requirement. The trace element interaction of highest practical significance in human nutrition is the negative effect of excess zinc on copper bioavailability.

Interaction of Zinc and Vitamin E in the Chick

Summary Chicks fed a low zinc diet (5 ppm) based on soybean protein, cornstarch, and corn oil developed severe skin lesions on the toes and foot pads as well as gross joint abnormalities that severely impaired locomotion. Incubation of foot skin in a peroxidative buffer containing 5 ppm Cu resulted in the release of malon-dialdehyde or other thiobarbituric acid reactive substances. The rate of release from skin or zinc deficient chicks was 4-5 times as great as from skin of controls fed adequate zinc. Supplementation of the zinc deficient diet with fat soluble antioxidants, particularly vitamin E, decreased the severity of the skin and joint pathology. High levels of dietary vitamin E also decreased the rate of release of peroxidative products from zinc-deficient skin but had no effect on control skin. The results show a significant physiological interaction between dietary vitamin E and zinc. It appears that cells from zinc-deficient chicks can benefit from incorporating higher than normal levels of vitamin E into their membrane structure. It is postulated that zinc protects against peroxidative damage and promotes membrane integrity.

Vitamin B12, a Factor in Prevention of Hydrocephalus in Infant Rats.

Summary After female rats, on a diet that contained soybean oil meal as a source of protein, became depleted of the factor that prevents hydrocephalus, the incidence of the abnormality among the offspring was 28%. The addition of a vit. B12 concentrate to the diet or the injection of crystalline vit. B12 in the dams during the early stages of gestation prevented the abnormality in the young animals and increased their viability. Hydrocephalus was not prevented by folic acid alone, but it has not been determined whether vit. B12 alone is effective or whether both folic acid and vit. B12 are required.

Connective tissue amine oxidase. I. Purification of bovine aorta amine oxidase and its comparison with plasma amine oxidase

Abstract 1. 1. Bovine plasma and aorta amine oxidase (amine: O 2 oxidoreductase (deaminating), EC 1.4.3.4) were purified approx. 60- and 170-fold, respectively. The aorta enzyme appeared to be non-mitochondrial, did not catalyze the oxidation of common short chain diamines and, in general, possessed properties previously described for plasma amine oxidase. 2. 2. In the n -alkylamine series, CH 3 (CH 2 ) n CH 2 NH 2 , the longer chain homologues were bound more tenaciously by both enzymes than the short chain homologues. 3. 3. The aorta enzyme was inhibited by chelating agents and activity could be partially restored by addition of Cu 2+ . Activity was lost when the aorta enzyme was incubated in the presence of cyanide, hydroxylamine, semicarbazide, isoniazid and iproniazid. 4. 4. Preparations of amine oxidase from aorta catalyzed the oxidation of peptidyl lysine when lysine-vasopressin was used as substrate, but the plasma enzyme was inactive. The polyamines, spermine and spermidine, also served as substrates for the aorta enzyme and, relative to benzylamine, they were oxidized at the same rates as when the oxidation was catalyzed by the plasma amine oxidase.

Maternal nutrition and hydrocephalus in newborn rats.

Summary Female rats were supplied with an experimental diet that contained soybean oil meal as a source of protein, and a vitamin mixture that included all recognized vitamins except ascorbic acid, niacin, folic acid and B12. The incidence of hydrocephalus in the young was less than 1%. When folic acid antagonist was added to this diet the incidence of hydrocephalus rose to 20%. The type of diet consumed during the pre-experi-mental period determined the amount of time that elapsed, during the experimental period, before hydrocephalus appeared in the young.