Sarcosine oxidation in mammals occurs via a mitochondrial dehydrogenase closely linked to the electron transport chain. An additional H 2 O 2 -producing sarcosine oxidase has now been purified from rabbit kidney. A corresponding cDNA was cloned from rabbit liver and the gene designated sox. This rabbit sox gene encodes a protein of 390 amino acids and a molecular mass of 44 kDa identical to the molecular mass estimated for the purified enzyme. Sequence analysis revealed an N-terminal ADP-␣-binding fold, a motif highly conserved in tightly bound flavoproteins, and a C-terminal peroxisomal targeting signal 1. Sarcosine oxidase from rabbit liver exhibits high sequence homology (25-28% identity) to monomeric bacterial sarcosine oxidases. Both purified sarcosine oxidase and a recombinant fusion protein synthesized in Escherichia coli contain a covalently bound flavin, metabolize sarcosine, L-pipecolic acid, and L-proline, and cross-react with antibodies raised against L-pipecolic acid oxidase from monkey liver. Subcellular fractionation demonstrated that sarcosine oxidase is a peroxisomal enzyme in rabbit kidney. Transfection of human fibroblast cell lines and CV-1 cells (monkey kidney epithelial cells) with the sox cDNA resulted in a peroxisomal localization of sarcosine oxidase and revealed that the import into the peroxisomes is mediated by the peroxisomal targeting signal 1 pathway.In mammals a variety of H 2 O 2 -producing oxidases including D-amino-acid oxidase, D-aspartate oxidase, L-hydroxy-acid oxidase, acyl-CoA oxidase, and L-pipecolic acid oxidase are compartmentalized in peroxisomes. The H 2 O 2 generated from these reactions is then converted to H 2 O and O 2 by the peroxisomal matrix enzyme catalase (1). Several disorders have been described in which there is a defect in peroxisomal assembly that results in a partial or total absence of peroxisomal functions (for a review see Ref.2). Patients with these peroxisomal disorders such as Zellweger syndrome, neonatal adrenoleukodystrophy, infantile Refsum disease, and hyperpipecolatemia all have elevated levels of L-pipecolic acid, an imino acid, which in human and monkey liver is oxidized by a peroxisomal L-pipecolic acid oxidase (3). Indeed, L-pipecolic acid oxidase activity was not detected in liver samples from patients with Zellweger syndrome (4). Primates dehydrogenate L-pipecolic acid to ␦-piperideine-6-carboxylate which is spontaneously converted to ␣-aminoadipic acid ␥-semialdehyde.The subcellular localization of this pathway seems to differ in other mammalian species. In rabbits, guinea pigs, dogs, and sheep L-pipecolic acid oxidation is primarily mitochondrial (5). However, during our studies examining the subcellular distribution of L-pipecolic acid oxidation in rabbits, a considerable amount of L-pipecolic acid oxidation was detected in the peroxisomes, in addition to the previously reported mitochondrial activity (6). Interestingly, this peroxisomal enzyme showed a high specific activity for sarcosine and also oxidized L-pipecolic acid and L-p...
This investigation shows that the reproducibility of uroflow measurements is limited. For their evaluation, anamnesis and the measured results have to be taken into account equally. We found correspondence of both parameters in about 50% only. One single measurement cannot provide precise information, as psychogenic, social, and other factors influence the measurement. In our study 3 subjects had their micturitions registered over a period of 2 months. We found an increase of the maximum flow with increasing bladder volume. The maximum bladder volume was reached in only four micturitions. Normal values range at about 25% of the maximum bladder volume. Analyzing the micturitions in regard to the time of day, we found maximum flow rates in the morning hours. Under clinical conditions the altered surroundings lead to a measured result which is psychogenically influenced and can only be balanced after repeated measurements. The curves of all 3 patients were equal and inconspicuous. In cases of infravesical obstruction, surgical success could be documented by comparing the pre- and postoperative uroflows. In all cases of neurogenic bladder disorders and unclear findings, uroflow measurements are, however, not sufficient, and diagnosis is accomplished by a complete urodynamic examination. In spite of certain restrictions, uroflowmetry yields a high level of information, besides being a simple, at any time reproducible, and noninvasive procedure. Due to its low costs, it should be the primary step in diagnostics in the clinic as well as for practitioners.
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