Masters Theses

Samuel Ebong

Date of Award

12-1991

Degree Type

Thesis

Degree Name

Master of Science

Major

Life Sciences

Major Professor

Walter R. Farkas

Committee Members

Donita Frazier, Bill Congdon

Abstract

Plasma amine oxidase (PAO; EC 1.4.3.6) is an important enzyme in the metabolism of naturally occurring amines. The enzyme is known to contain copper and is generally believed to be present in the plasma of all higher mammals. Earlier evidence pointed to pyrroquinoline quinone (PQQ) as the cofactor required for its function. However, the latest findings indicate that 6 - hydroxydopa may be the true cofactor. PAO will oxidize only primary, medium to long chain amines, and is sensitive to cyanide. The other amine oxidases (mainly cellular) are known to oxidize both primary and secondary amines and are not sensitive to cyanide. We initiated studies to determine the effect of nutritional deficiencies on the plasma enzyme in mice and were surprised to find that control mice fed a normal diet lacked functional PAO. Since the mouse is one of the most frequently used animal models and many compounds of pharmacological and toxicological interest are amines, we initiated a study to find out if sera from eleven different mammals could oxidize a group of amines of biomedical interests. The study used three main assays: benzylamine assay, paper chromatography assay, i.e., determination of the disappearance of reactants, and the assay for the release of ammonia. Our results indicate that the enzyme is not present in all higher mammals. Furthermore, substrate specificity varies from species to species. It is generally believed that polyamines are the natural substrates for this enzyme. However, neither putrescine, spermidine or spermine, the three major polyamines, were oxidized by mouse serum. Furthermore, the absence of PAO activity in mouse serum is not due to the presence of an inhibitor since mouse serum did not inhibit the oxidation of amines by rabbit, cow, or human.

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