Search

We herein report a case of Klebsiella oxytoca-producing IMP-1 that was detected as a first isolate of carbapenem-resistant Enterobacteriaceae (CRE) at our facility. Since K. oxytoca is an uncommon strain for CRE, we speculated that the resistant organism had already spread out inside the hospital. Metallo-β-lactamases promotes antibiotic resistance in Enterobacteriaceae, which potentially yields problematic issues in clinical settings. Active surveillance of antibiotic resistant strains is important and should be repeatedly highlighted. Furthermore, appropriate methods should be established to detect highly resistant strains.

Trypanosomatid protozoan pathogens are purine auxotrophs that are highly dependent on the enzyme inosine monophosphate dehydrogenase (IMPDH) for the synthesis of guanylate nucleotides. Enzymatic characterization of the Leishmania donovani IMPDH (LdIMPDH) overexpressed in E. coli revealed that this enzyme was highly specific for the substrates IMP and NAD(+) with K(m)(app) values of 33 and 390 microM, respectively. In contrast to other IMPDHs, LdIMPDH exhibits no substrate inhibition in high concentrations of NAD(+). Kinetic studies revealed that XMP and GMP were inhibitors with K(i) values of approximately 26 and 210 microM, respectively, suggesting that these nucleotides may regulate LdIMPDH activity. Mycophenolic acid was also a potent inhibitor of L. donovani IMPDH with a K(i) value of approximately 25 nM. Confocal immunofluorescence microscopy and subcellular fractionation localized LdIMPDH to the glycosome. Protein-protein interaction assays revealed that LdIMPDH associated tightly with glycosomal protein sorting receptor LdPEX5.

Previous work has shown that the crude venom of Parawixia bistriata induces convulsive seizures in rats after intracerebroventricular injection. In this work, the isolation of a bioactive fraction with ultraviolet absorption characteristics of nucleic acid and trace protein or amino acid content is described. NMR analysis demonstrated that the major component of the active fraction is the nucleoside inosine. An analogue of this component (inosine 5'-monophosphate) induced a delayed paralysis effect in termites.

1. A rapid method for the determination of AMP and IMP by HPLC is described. 2. Its application to the assay of AMP deaminase allows the specific determination of enzyme activities in crude extracts, eliminating any interference by other enzyme systems (5'-nucleotidase and adenosine deaminase). 3. The method was routinely used for the determination of the AMP deaminase activity in the muscles of marine animals.

The effect of variation in the concentration of inorganic phosphate and of the pyridine precursors nicotinamide (NAm) and nicotinic acid (NA) on pyridine nucleotide synthesis was studied using intact human erythrocytes. A wide range of incubation times was employed. The results showed that under physiological conditions the rate of synthesis of NAD from NAm exceeded that from NA twofold, while the reverse situation pertained at higher and unphysiological substrate levels. The two pathways had different regulation points. For NAm the rate-limiting factor was the initial step, namely its conversion into the mononucleotide, while for NA it lay at the second step, conversion of NA mononucleotide (NAMN) to its adenine dinucleotide. At physiological substrate levels the uptake of NA and conversion to NAMN were rapid, while the uptake and conversion of NAm were time dependent. This process was stimulated significantly by inorganic phosphate only for NAm. These results indicate that while NA is the predominant precursor of human erythrocyte NAD at high (unphysiological) substrate and phosphate levels, NAm is more efficient as an NAD precursor under physiological conditions, suggesting an important and hitherto unrecognized role for nicotinamide in NAD synthesis in vivo.

This study examined the dynamics for ammonia (NH3) metabolism in human skeletal muscle during and after intense one-legged exercise. Subjects (n = 8) performed dynamic leg extensor exercise to exhaustion (3.2 min). Muscle NH3 release increased rapidly to a maximum of 314 +/- 42 mumol/min and declined immediately on cessation of exercise. Recovery was complete in approximately 20 min. Arterial [NH3] increased less rapidly and reached its maximum 2-3 min into recovery. These data demonstrate that NH3 clearance is more sensitive to the cessation of exercise than is NH3 release from skeletal muscle. Muscle [NH3] increased three to fourfold during exercise and represented 74 +/- 8% of the total net NH3 formation. Thus the change in muscle [NH3] alone underestimates the NH3 production. There was no evidence that the muscle-to-venous blood NH3 ratio shifts in accordance with the H+ data. Thus other factors must contribute to the NH3 release from active muscle. The total net NH3 formed corresponded with the intramuscular inosine 5'-monophosphate accumulation, suggesting that the NH3 was derived from AMP deamination. Changes in the known modulators of AMP deaminase (ATP, ADP, H+) were moderate, so the mechanisms initiating the deamination remain obscure.