Carl M. Lyman

Preliminary report on the nutritional significance of bound gossypol in cottonseed meal

SummaryA procedure is described by which bound or inactivated gossypol can be removed from cottonseed meal without the application of heat which might damage the protein. The removal of bound gossypol increased the nutritional value of the protein as determined by chick feeding tests, rat protein-repletion tests, and lysine availability tests. A procedure is described for the preparation of a gossypol-cottonseed protein complex without heating the materials. As a result of the combination of the protein with gossypol, marked reduction in nutritional value occurred. The nitrogen solubility of the complex was only about half that of the original protein. The results are in accord with the concept that the inactivation of gossypol during the processing of cottonseed meal is accomplished through the formation of an insoluble, inert gossypol-protein complex which results not only in rendering the gossypol harmless but also in the loss of part of the nutritional value of the protein.

Reaction of gossypol with amino acids and other amino compounds

The reactions of gossypol with certain amino acids and other amino compounds have been studied spectroscopically with respect to the effect of time and pH in the range from 5.7 to 7.5 at 37 C. The rate of reaction of gossypol with amino acids increases with increase in pH and has been shown to be related to the distance of the amino group from the carboxyl group within the molecule. Reaction products of gossypol with amino acids and other amino compounds were subjected to various purification procedures and analysis to determine combination ratios. In addition to the expected gossypol-to-amino compound ratio of 1:2, dictated by the formation of Schiff base-type bonds with the two aldehyde groups of gossypol, compounds with ratios of 1:3 and 1:4 were isolated. These results indicate that each of the two aldehyde groups of gossypol can react with two amino groups under the conditions studied.

Metabolism of gossypol in the chick

Abstract14C labeled gossypol was administered to young chickens and the deposition of gossypol plus gossypol decomposition products in the various tissues was evaluated by determination of14C activity in a scintillation spectrometer. Most of the gossypol activity was recovered in the feces with relatively smaller amounts retained by the tissues. Most of the labeled compound retained was found in the liver, muscle, blood and kidneys, with the highest concentration in the liver. Increasing the protein content of the diet by the addition of fish meal reduced the amount of gossypol plus gossypol decomposition products found in the tissues.

Metabolic fate of gossypol: The metabolism of gossypol-14C in laying hens

Abstract Orally administered formyl-14C-labeled gossypol was rapidly excreted by laying hens into the urine and feces. Only a small portion was deposited in the tissues. A major part of the absorbed gossypol was concentrated in the eggs. The excretion of gossypol into the intestine via the bile seemed to be a major pathway by which absorbed gossypol was excreted. The decarbonylation of gossypol to carbon dioxide and apogossypol was not a major route for gossypol metabolism in the laying hen. The time necessary to eliminate one-half of the radioactive gossypol (10 mg, 0.35 μCi) from the bird body (1 kg) under the conditions used was found to be 30 hr.

An aminotransferase specific for the d-enantiomorph of methionine

Abstract An enzyme was isolated from germinating peanut seed and shown to be an aminotransferase specific for the d -enantiomorph of methionine. The keto acid of methionine, α-keto-γ-methylthiobutyrate, was isolated from the reaction mixture and identified. Of the keto acids tested pyruvic acid was the most effective acceptor for the amino group of methionine. A small amount of enzyme was isolated which gave only one band on disc gel electrophoresis.

Effect of bound gossypol in cottonseed meal on enzymic degradation

The nutritive value of cottonseed protein is lowered by the presence of bound gossypol. Samples of cottonseed protein containing from 0.003% to 1.03% bound gossypol were hydrolyzed enzymically and the amounts of free amino acids released were determined. The amounts of amino acids contained in peptides not precipitated by 1% picric acid were also determined. The proportionate reduction in the release of free and peptide amino acids in the presence of bound gossypol was noted. Although the amount of lysine released is reduced in the presence of bound gossypol as expected, there is a markedly larger reduction in the release of a number of other amino acids.