The end product of purine metabolism varies from species to species. The degradation of purines to urate is common to all animal species, but the degradation of urate is much less complete in higher animals. The comparison of subcellular distribution, intraperoxisomal localization forms, molecular structures, and some other properties of urate-degrading enzymes (urate oxidase, allantoinase, and allantoicase) among animals is described. Liver urate oxidase (uricase) is located in the peroxisomes in all animals with urate oxidase. On the basis of the comparison of intraperoxisomal localization forms, mol wt, and solubility of liver urate oxidase among animals, it is suggested that amphibian urate oxidase is a transition form in the evolution of aquatic animals to land animals. Allantoinase and allantoicase are different proteins in fish liver, but the two enzymes form a complex in amphibian liver. The subcellular localization of allantoinase and allantoicase varies among fishes. Hepatic allantoinase is located both in the peroxisomes and in the cytosol in saltwater fishes, and only in the cytosol in freshwater fishes. Hepatic allantoicase is located on the outer surface of the peroxisomal membrane in the mackerel group and in the peroxisomal matrix in the sardine group. Amphibian hepatic allantoinase-allantoicase complex is probably located in the mitochondria. On the basis of previous data, changes of allantoinase and allantoicase in molecular structure and intracellular localization during animal evolution may be as follows: Fish liver allantoinase is a single peptide with a mol wt of 54,000, and is located both in the peroxisomes and in the cytosol, or only in the cytosol. Fish liver allantoicase consists of two identical subunits with a mol wt of 48,000, and is located in the peroxisomal matrix or on the outer surface of the peroxisomal membrane. The evolution of fishes to amphibia resulted in the dissociation of allantoicase into subunits, and in the association of allantoinase with the subunit of allantoicase. This amphibian enzyme was lost by further evolution.

It is generally accepted that all of the allantoin-degrading enzymes (allantoinase, allantoicase, ureidoglycollate lyase and urease), used in purine degradation, were lost during mammalian evolution. However, surprisingly, ureidoglycollate lyase has been found in a mammalian tissue. Ureidoglycollate lyase was purified to homogeneity and characterized from rat-liver mitochondria. The apparent Km (17 mM) of the rat enzyme for ureidoglycollate was much higher than that (0.33 mM) of fish-liver ureidoglycollate lyase. The rat-liver enzyme differed from the fish-liver enzyme in enzymic, physical and immunological properties.

Tribological properties of over-based and neutral calcium sulfonate were examined under boundary lubrication conditions by using a ball-on-flat type tribo-tester. It was found that over-based calcium sulfonate reduced friction and wear of steel-steel contacts, whereas the neutral calcium sulfonate did not. It was found that boundary film composed of calcium oxide plays significant role on improving the tribological properties. Surface analyses by XPS and Time-of-flight secondary mass spectroscopy (TOF-SIMS) revealed that the major component of the film on upper surfaces is calcium carbonate and that at subsurfaces are composed of calcium oxide. A depth profile of the film obtained by TOF-SIMS using an etching technique revealed that thickness of the film is up to 240 nm. A static pyrolysis of the over-based calcium sulfonate on steel surface affords a thin film composed of calcium oxide, indicating that rubbing process is essential for the formation of the boundary film.

Glutamate:glyoxylate aminotransferase had been reported to be present exclusively in the peroxisomes of plant leaves and to participate in the glycollate pathway in leaf photorespiration (Tolbert (1971) Annu. Rev. Plant Physiol. 22, 45-74]. Glutamate:glyoxylate aminotransferase activity was already present in the etiolated cotyledons of cucumber (Cucumis sativus) seedlings, and increased during greening. The enzyme was present only in the cytosol of the etiolated cotyledons and appeared in the peroxisomes during greening. The enzyme was purified to homogeneity from the cytosol of the etiolated cotyledons and from the peroxisomes of the green cotyledons of cucumber seedlings. The two enzyme preparations had nearly identical enzymic and physical properties. On the basis of these findings, roles of glutamate:glyoxylate aminotransferase in the glycollate pathway in photorespiration, and the mechanism of its appearance in the peroxisomes during greening, are discussed.

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