Abstract
SUMMARY 1. Studies of the phosphate activation of glutaminase activity (glu- taminase I), hitherto studied in the tissues of the rat, have been extended to include other species. 2. The glutaminase activity at pH 8.0 in aqueous extracts of rat and mouse kidney, liver, brain, and spleen and of rabbit and guinea pig brain and spleen is greatly increased by added phosphate. Under the same conditions, the glutaminase activity of extracts of rabbit and guinea pig kidney and liver and of the sedimentable fraction of rabbit and guinea pig liver is only slightly increased by added phosphate. 3. Studies of the effect of various phosphate concentrations on the desamidation of glutamine in extracts of rat kidney revealed that a higher concentration of phosphate was necessary to achieve an appreciable ac- celeration of desamidation than was the case in extracts of brain or liver. The concentration of phosphate required to yield maximum acceleration
Highlights
hitherto studied in the tissues of the rat
of rabbit and guinea pig brain and spleen is greatly increased by added phosphate
of the sedimentable fraction of rabbit and guinea pig liver is only slightly increased by added phosphate
Summary
Subsequently noted that an appreciable phosphate and arsenate activation of rat kidney glutaminase can be demonstrated in extracts more diluted, and at concentrations of phosphate or arsenate more elevated, than those employed heretofore. The characteristics of this activation, and extension of the phenomena to other tissues in various species, are described. Sodium hydrogen phosphate or arsenate was dissolved in this buffer when desired, and the pH subsequently adjusted with either NaOH or HCl. Glutamine solutions in distilled water were prepared daily. No measurable ammonia was evolved in digests of extracts which were heated at 100” for 10 minutes, cooled, and incubated 1 hour at 37” with glutamine and phosphate (cf. (1))
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