Conversion of citrulline to ornithine by cell-free extracts of Streptococcus lactis

SYNOPSIS. Studies on the metabolism or arginine, citrulline, and ornithine by Tetrahymena pyriformis confirmed that these compounds do not participate in a urea cycle in this organism. No evidence for the enzymes of the cycle or for the presence of urea or urease was found. However, conversion of arginine to ornithine takes place. This system consists of two enzymes, arginine desimidase and a citrulline‐hydrolyzing enzyme. This is different from the arginine dihydrolase enzymes reported for bacteria and yeast, since no labile phosphate is produced in the conversion of citrulline to ornithine. The enzyme responsible for the latter conversion was purified 44‐fold. The pH optimum of the enzyme, its substrate specificity, and the effect of inhibitors on its activity were investigated. The enzyme appears entirely hydrolytic in nature.

Section: Pyriforniiscontrasting

confidence: 88%

The Relationship between Arginine, Citrulline and Ornithine in *Tetrahymena pyriformis**

1965

“…An enzyme capable of acting on citrulline yielding stoichiometric amounts of C 0 2 , ammonia and ornithine was found in the cell extracts of all 5 Herpetonionas tested ( Table 5 ) . The hydrolysis of citrullinc by cell extracts of Herpetomonas was similar to that reported in Tetrahymena (14) and thus different from the coupled OCT-carbamate kinase degradation of citrulline effected by other microorganisms (18,38). The enzyme of Herpetomonas did not require exogenous ADP, Mg2+ and cell extracts could be extensively dialyzed or filtered through Sephadex G-25 for the removal of low-molecular substances without loss of enzyme activity.…”

Section: Citrulline Hydrolasesupporting

confidence: 59%

“…That an O C T was not involved either was suggested by inhibition of production of CO, upon addition of arsenate to the mixture. Contrary results should be obtained were OCT involved (18). Moreover, while the O C T of Hei-petomonas was inhibited by fluoride, production of CO, from citrulline was not and while O C T was not affected by heating the cell extracts at 55 C for 30 min the ability of those extracts to promote hydrolysis of citrulline was completely destroyed within 10 min.…”

Section: Citrulline Hydrolasementioning

confidence: 66%

Enzymes of the Ornithine‐Arginine Metabolism of Trypanosomatids of the Genus *Herpetomonas**

Yoshida¹,

Jankevicius²,

Roitman³

et al. 1978

XtDrparlanirnto tfe N i r ? o , Imuno e Parasttologin, E~t o l a PaitliJta tle Aledrcina. 1%. Uoturatu 862, Sdo Paulo, S.P. and ~D e~i t i i tarnento tie Biologin Celitlai , 1Jna~e~sidade de Brasilia, Brasilia, DF, Brasil SYNOPSIS. Five strains of trypanosnniatids. Herpetomonas megaseliae. H . samuelpessoai, H . muscarurn muscarurn, H . muscarum ingenoplastis and a newly isolated Herpetonionas sp., were exatnined for the enzymes of arginine-ornithine metabolism. Ornithine rarbamoyltransferase (E.C. 2.1.3.3 ) and argininosuccinate lyase (E.C. 4.3.2.1) were detected in cell extracts of H . mega.reliae, H . samuelpessoai and H . ~n~~c a r u i i i muscarurn but not of others. Both enzymes seemed repressible by arginine, lvhich could account for their apparent absence in H . muscarurn ingenoplastis and Herpetomonas sp., which grow in a complex, arginine-rich medium. r\dditionally, arginine deiminase (E.C. 3.5.3.6) and citrulline hydrolase were detected in cell extracts of the 5 strains exaniincd. This latter cnzyrne. previously described only in Tetrahj'tnena, effects the single-step hydrolysis of citrulline into ammonia. ornithine and CO,. Arginase (E.C. 3.5.3.1) and urease (E.C. 3.5.1.5) were not found in any of the strains examined. Some of the physicochemical characteristics of the enzymes encciuntered are described.

“…Kidder et al ( 8 ) had conjectured that in C. fasciculata a "phosphorolytic citrullinase" acting on citrulline would yield ornithinc + carbamyl phosphate. In bacterial systems a coupled OCT-carbamate kinase reaction effects such a conversion ( 11 ) . But since Crithidia do not have OCT, this possibility seems unlikely.…”

mentioning

confidence: 99%

Enzymes of the Ornithine‐Arginine Metabolism of Trypanosomatids of the Genus *Crithidia**

Figueiredo

Yoshida

Roitman

et al. 1978

SYNOPSIS. Twelve strains of Crithidia, which fall into 8 species, were tested for occurrence of enzymes of ornithine‐arginine metabolism. The following enzymes were investigated: arginase, ornithine carbamoyltransferase, argininosuccinate lyase, citrulline hydrolase, arginine deiminase and urease. Arginase and argininosuccinate lyase were found in all species. Citrulline hydrolase was also found in all but the 2 strains carrying endosymbiotes C. deanei and C. oncopelti. On the other hand, ornithine carbamoyltransferase was found only in these 2 strains. Arginine deiminase and urease were absent in all strains. The existence of a common enzymatic pattern for species of the genus Crithidia is thus reported.