Cxxxviii. Studies in Tissue Metabolism. Vi. Lactic Dehydrogenase, Xanthine Oxidase and Nucleosidase in Tumour and Muscle Extracts

IN a previous communication [Boyland and Boyland, 1934] two distinct lactic dehydrogenases were described, one present in yeast and one in mammalian muscle. Tumour tissue (Jensen rat sarcoma) extracts made by the method previously used with muscle reduced methylene blue rapidly in the presence of lactic dehydrogenase coenzyme (prepared after Banga et al. [1932]) in the absence of any other substrate. Extracts of J.R.S. were also made by the method of freezing and thawing described by Boyland and Mawson [1934] with similar results. No amount of washing of the tissue or dialysis of the extract appeared to reduce the activity. In some cases the time of reduction of methylene blue was slightly decreased by the addition of lactate but the differences appeared to bear no relation to the time of dialysis, which precluded the possibility that the extract was acting on some dialysable substrate which it contained. Similarly extracts of rat and mouse muscle contained some lactic dehydrogenase but also reduced methylene blue without the addition of lactate. Some typical results for muscle extracts are given in Table I. All the results described in this paper were obtained by observation of the time necessary to decolorise methylene blue solution in evacuated Thunberg tubes at 380.