Rhizobium etli mutants unable to grow on asparagine as the nitrogen and carbon source were isolated. Two kinds of mutants were obtained: AHZ1, with very low levels of aspartase activity, and AHZ7, with low levels of asparaginase and very low levels of aspartase compared to the wild-type strain. R. etli had two asparaginases differentiated by their thermostabilities, electrophoretic mobilities, and modes of regulation. The AHZ mutants nodulated as did the wild-type strain and had nitrogenase levels similar to that of the wild-type strain.Amino acid synthesis has been studied in various microorganisms; amino acid degradation has been less studied, despite the fact that the intracellular amino acid concentration must be the result of its synthesis and degradation. In Neurospora crassa and Rhizobium etli, it has been shown that the intracellular glutamine concentration is the result not only of the regulation of the synthesis but also of the degradation of this amino acid (4, 6-8, 15, 16, 31). To determine if the intracellular concentrations of other amino acids are regulated in the same way as that of glutamine, we decided to study the degradation of asparagine (an amino acid very similar to glutamine, with four carbon skeletons instead of five) in R. etli, a bacterium that establishes symbiosis with Phaseolus vulgaris (39).In R. etli, L-asparagine can be utilized as the sole carbon and nitrogen source through the action of two enzymes (20). The first enzyme, asparaginase (EC 3.5.1.1), catalyzes the hydrolysis of L-asparagine to L-aspartate and ammonium. The second enzyme, L-aspartase (EC 4.3.1.1), catalyzes the reversible deamination of L-aspartate to yield fumarate and ammonium. R. etli asparaginase is found to be positively regulated by its substrate asparagine and negatively regulated by the carbon source; it is not regulated by the amount of oxygen dissolved in the growth medium or by nitrogen catabolite repression, and some asparaginase activity is detected when R. etli is grown on ammonium as a nitrogen source and succinate as a carbon source (20). Asparaginase has been studied in other gramnegative bacteria such as Escherichia coli (10,12,22,24,25,37,47), Salmonella enterica (23), Erwinia chrysanthemi (19), and Vibrio proteus (41) and in gram-positive bacteria such as Bacillus subtilis (1, 21, 43) and Staphylococcus aureus (35,42).R. etli aspartase was found to be positively regulated by asparagine, negatively regulated by the carbon source and by ammonium, and not regulated by the amount of oxygen dissolved in the growth medium (20). L-Aspartase has been studied in other bacteria such as E. coli (25,27,33,36), B. subtilis (43), Pseudomonas fluorescens (30, 45), and Serratia marcescens (44).In this report, we describe the isolation and characterization of R. etli mutants altered in the degradation of asparagine, present evidence that R. etli has two asparaginases, and investigate the regulation of these isoenzymes. The cloning of an R. etli DNA fragment that complements the isolated mutants is also reported...
ABSTRACT:We here report acute pancreatitis with multiorganic complications in a female Cocker Spaniel. The most important alterations in clinical pathology were renal azotaemia, hyperbilirubinaemia with a prevalence of conjugated bilirrubin and increased alkaline phosphatase by cholestasis; hyperamylasaemia due to pancreatitis; dehydration, hyponatraemia, hypochloraemia and hypokalaemia related to vomiting; metabolic acidosis and respiratory alkalosis corresponding to mixed acid-base disorder; markedly regenerative anaemia with spherocytes and agglutination due to immune-mediated haemolytic anaemia and intravascular haemolysis; leukocytosis with a left shift. Proteinuria, glucosuria, bilirubinuria and haemoglobinuria were detected in the urine. Severe suppurative pancreatitis with peripancreatic necrosis and suppurative esteatitis, tubulorrhectic nephrosis, severe hepatitis and intrahepatic cholestasis corresponded with alterations described by clinical pathology. In order to diagnose acute pancreatitis in dogs with multiple complications, it is very important to integrate the results of clinical pathology with the anamnesis and physical examination of the animal. It is especially important to note that the serum activity of amylase correlates with time after the pancreatic attack.
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