Homogeneous amidophosphoribosyltransferase (EC 2.4.2.14)preparation was obtained from chicken liver. The enzyme preparation was effectively stabilyzed with PRPP or Pi in the presence of Mg²+. From the result of sodium dodecyl sulfate-polyacrylamide gel electrophoresis, the subunit molecular weight was estimated to be approximately 58,000. In Tris-Cl buffer, the predominant form of the enzyme had an ^s20, ω of 6.5, Stokes radius of 40Å, and estimated molecular weight of 110,000. Incubation with PRPP or Pi resulted in an increase in the ^s20, ω to 9.1-9.5, Stokes radius to 50Å, and estimated molecular weight to 200,000. Incubation of the larger form with AMP led to a decrease in the molecular weight of the enzyme. One-millimoler AMP produced sigmoidal kinetics with respect to the substrate PRPP, with Hill coefficient of 1.8. Inorganic phosphate inhibited the enzyme activity competitively with respect to the substrate PRPP. It is concluded that chicken liver amidophosphoribosyltransferase is an allosteric protein whose activity is regulated by a series of conformational changes induced by a number of ligands.

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The effects of a high protein diet on purine metabolism in gouty and non-gouty chickens were compared. The daily urinary urate excretion were compared in gouty and non-gouty chickens fed a high protein (40%) and a normo protein (17%) diets. The daily urinary urate excretion in gouty chicken on high protein diet was more than that in non-gouty ones. The activities of six enzymes involved in purine metabolism (G-PRPP-AT, PRPP synthetase, glutamine synthetase, HGPRT, APRT and xanthine dehydrogenase) in the livers of gouty and non-gouty chickens on high and normo protein diets were also compared. The activities of G-PRPP-AT and glutamine synthetase in gouty chicken were more highly induced by a high protein diet than in non-gouty ones. In contrast, HGPRT and APRT activities in gouty chicken were decreased by a high protein diet while those in non-gouty ones were increased. A high protein diet induced PRPP synthetase and xanthine dehydrogenase in similar extent in gouty and nongouty chickens. The hepatic contents of PRPP, glutamine, oxypurine and urate were estimated. A high protein diet increased the hepatic PRPP content both in gouty and non-gouty chickens. On the other hand, the hepatic glutainine content in gouty chicken was decreased by a high protein diet, but not in non-gouty ones. Increase of urate content in the liver was observed only in gouty chicken, and it was twice in nongouty ones. These results suggest that the excessive supply of glutamine is one of the important factors in the accelerated purine and urate biosynthesis in gouty chicken.

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Primary immunodeficiencies with defects of purine salvage enzymes have been recently reported. The facts that adenosine deaminase (ADA) deficiency is associated with both Tand B-cell dysfunctions but that purine nucleoside phosphorylase (PNP) deficiency is associated with only T-cell dysfunction lead to a working hypothesis that each type of these immunodeficiencies might result from the difference of the regulatory mechanism on purine metabolism between Tand B-cells. In order to testify this hypothesis, PNP activities as well as ADA activities were determined in T- and B-cells obtained by rosette-forming with sheep red blood cells (E)and antibody and complement coated sheep red blood cells (EAC), respectively. The activities were assayed biochemically and by a newly developed histochemical method. PNP activity biochemically assayed with T-cells was about 3-times higher than that with B-cells. ADA activity in Tcells was about 2-times higher than that in B-cells. Histochemical PNP and ADA stainings showed higher activities in T-cells than B-cells. The difference of PNP staining activity between T- and B-cells was found to be larger than that of ADA staining activity. These results suggest that PNP is more necessary for the function of T-cells than B-cells. A part of uric acid in sera is derived from purine bases produced by lymphocyte. T-cells with higher PNP and ADA activities take a greater part in uric acid production than B-cells with low PNP and ADA activities.

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In 22 patients with hyperuricemia, measurements of the CH₅₀, the proteins of complement-system, proteinase inhibitors, plasminogen and fibrinogen in the blood were carried out, in order to find out pathophysiological response into sodium urate deposition. Significant increase of C₄, C₃, C₃-Activator and fibrinogen was generally present in patients with hyperuricemia as compared to normal control. In patients with previous history of gouty attack, these changes became more prominent and CH₅₀ and C_1q also showed significant increase. The documentation of these finding which were obtained in non-acute phase, suggests us the presence of more or less pathophysiological changes in the background of hyperuricemic patients. And study of these complement activity and proteins in the blood might be significant procedures to support diagnosis ot so-called asymptomatic nyperuricemia.

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Uric acid is the end-product of purine metabolism, and the purines are nitrogenous bases derived from the breakdown of nucleic acids. It was presented by the authors at the Eighteenth Annual Meeting of the Japanese Society of Neurology in Nagoya, May 18,1977, that CSF uric acid levels were increased in patients with histologically malignant brain tumor. Responsible factors for increased CSF uric acid levels are thought to be (1) increased permeability of blood-CSF barrier; (2) cerebral cell necrosis; and (3) increased turnover of the nucleic acid. The purpose of this paper is to find out the diagnostic value of CSF uric acid levels in patients with brain tumor compared with CSF lactate dehydrogenase activities. CSF uric acid levels and lactate dehydrogenase activities were investigated in 30 cases of normal control and in 52 cases of brain tumor. The mean values and standard deviations of CSF uric acid levels and lactate dehydrogenase activities were as follows in normal controls.Increased CSF uric acid levels and lactate dehydrogenase activities over the age of 50 are thought to be due to cerebral cell necrosis. Both CSF uric acid levels and lactate dehydrogenase activities were increased in histologically malignant brain tumors with numerous mitotic figures such as grade III-IV astrocytoma, medulloblastoma and sarcomatous meningioma. But, there is a strange phenomenon named “paradoxical normalization”. It is a phenomenon that both CSF uric acid levels and lactate dehydrogenase activities are normalized in histologically malignant brain tumors with cyst formation. CSF uric acid levels were not influenced by increased intracranial pressure. But CSF lactate dehydrogenase activities were more easily influenced and increased in almost all cases above 400 mm H₂O, even if these cases were histologically benign. Uric acid levels and lactate dehydrogenase activities were investigated in the cyst fluids of brain tumor. Both of them were more concentrated in the cyst fluid than in the CSF. In the malignant brain tumor, uric acid levels and lactate dehydrogenase activities in the cyst fluids were higher than the serum levels. But in the benign brain tumor, they were lower than the serum levels.

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In the presence of Cu²⁺, ascorbate decomposes histamine in citrate phosphate buffer (pH 6.5). The breakdown is completely inhibited by catalase, but only slightly by superoxide dismutase, and scanvenger of OH. Addition of H₂O₂ to the reaction mixture markedly enhances the rate of histamine breakdown by ascorbate. However, H₂O₂ alone cannot breakdown histamine even in the presence of Cu²⁺. Therefore, it is concluded that the combination of H₂O₂ and monodehydroascorbic acid, both of which are produced during the autooxidation of ascorbate, plays a major role in the histamine transformation. Ascorbic acid cannot be replaced by equimolar concentration of uric acid, in the system of histamine breakdown, while the latter, along with other purine derivatives, blocked ascorbate-induced histamine transformation. Detailed mechanisms in respect to the inhibitory effect of urate on ascorbate-induced histamine breakdown are now in progress in our laboratory.

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