Cadmium- or zinc-binding to bone lysyl oxidase and copper replacement

Lysyl oxidase was purified to about 3,000- to 5,000-fold from epiphyseal cartilages of chick embryos. Purification was accomplished by sequential column chromatographies of collagen-sepharose, DEAE-Cellulose and Sephacryl S-200. The molecular weight of the most purified enzyme from 4 different isomers as determined by gel-filtration technique using Sephacryl S-200 column was 32,000 and the purified enzyme contained one copper atom per mole. When the enzyme (copper content: 1.12 g-atom per mole) was incubated with 1 X 10(-4)M cadmium, followed by gel-filtration, 0.12 g-atom of cadmium was incorporated into the enzyme per mole and consequently 0.23 g-atom of prosthetic copper was released from the enzyme (loss of 21%) with a substantial decrease of the enzyme activity by 22.8%, but 50% loss of copper caused by treatment with 1 X 10(-3)M cadmium did not further decrease the activity. When the enzyme was incubated with 1 X 10(-4)M zinc, 0.38 g-atom of zinc bound to the enzyme and 65% copper was lost, resulting in 34% loss of the activity. Loss of 84% copper (experiment with 1 X 10(-3)M zinc), however, led to 47% inhibition. These findings indicate the existence of metal-metal interaction in the enzyme that can significantly influence the activity, though inhibition of the enzyme was not strictly proportional to either the amount of copper released or the amount of cadmium or zinc bound to the enzyme.