An examination of the putative glucose tolerance factor activity of amino acid and peptide fractions isolated from brewer's yeast : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Chemistry at Massey University

Abstract

The first report of the possible existance of a glucose tolerance factor (GTF) was made by Mertz and Schwarz (1955) who noticed that a dietary additive, termed factor 3, isolated from an enzymatic casein hydrolysate (Schwarz (1952)), maintained normal glucose removal rates in diabetic­ like rats. These rats were the subject of a study on the development of dietary necrotic liver degeneration. The immediate cause of death,,in these rats, could be demonstrated to be severe hypoglycaemia (Mertz and Schwarz (1955)) that initially manifested itself, during the latent period of degeneration, as impairment of excess blood glucose removal. The diet used to induce the development of necrotic liver degeneration was a semi-purified, vitamin E-free, ration of 30% Torula yeast which also represented the sole protein source. The vitamin E prevented the development of necrotic liver degeneration but did not affect the removal of excess blood glucose. In 1957, Schwarz and Mertz reported that the factor 3, in itself, was not responsible for the maintainance of normal glucose removal rates but rather that it contained an active fraction separable by fractionation procedures involving evaporation, in vacuo, of a NaCl-containing, factor 3 concentrate. The NaCl was removed by filtration and the GTF activity was found to be present in the separated salt fraction, from which it could be removed by treatment with 65% ethanol. A further claim was made that this separated substance, now termed the glucose tolerance factor (GTF), not only prevented but cured impairment of glucose removal when administered in the diet and that the initial glucose impairment observed was not a symptom of necrotic liver degeneration but a result of a dietary deficiency. GTF prepara­ tions were reported (Mertz and Schwarz (1959)) to be routinely obtained from brewer's yeast as well as acid hydrolysates of dried, defatted, pork kidney powder. [From Introduction]