Abstract
The iodination of lactate dehydrogenase isoenzymes which has not been attempted so far has been performed using radioactive and inactive iodine. A new method for the determination of trace amounts of protein-bound iodine in the range of 10–100 μg has been developed. Out of two methods employed for iodination, chloramine-T method was found to be superior to the lactoperoxidase method for iodination with both radioactive and inactive iodine. It was found that the amount of iodinated LDH formed during iodination depends on the amount of LDH and of the reagents used for iodination. Completely purified LHD-1 and LDH-2 isoenzymes were iodinated using both inactive and radioactive iodine. The iodinated isoenzymes were separated from the unreacted iodide by gel permeation chromatography using Sephadex G-75-120 column. The ratio of radioiodinated LDH to unreacted125I was largest (3.72) when the amount of LDH used was 4.54 μg. The specific activity obtained when iodination was carried out under optimum conditions was 238 μCi/μg. No radiation damage for the radioiodinated LDH was observed when it is kept for as long as two weeks after iodination.
Published Version
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