The isolation of l-thyroxine from the thyroid gland by the action of proteolytic enzymes

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Abstract
A method, which employs pepsin, was described for isolating thyroxine. The thy-roxine was levorotatory, and had a specific rotation of [a]5461[long dash]38 as the sodium salt in 60% alcoholic solution. The digestion product (1.3 mgm. per diem for 6 days of a preparation containing 50% of I) produced an increase in O consumption of 85% in the rat when given orally, while pure l-thyroxine had no effect. There was less physiological difference when they were injected subcutaneously. Trypsin did not liberate I from diio-dotyrosine within 5 mos. Several methods were described which showed how the early stages of the digestion of thyroid gland by pepsin and trypsin was carried out. The purified digestion product consisted of a mixture of free thyroxine with thyroxine peptides.