Berlin, Technische Universität Berlin, Diss., 2013
Berlin, Technische Universität Berlin, Diss., 2013
Berlin, Technical University of Berlin, Diss., 2013
Plasmalogenase in hamster heart Arthur, G; Covic, L; Wientzek, M ...
Biochimica et biophysica acta,
02/1985, Letnik:
833, Številka:
2
Journal Article
Recenzirano
In this study, the presence of plasmalogenase for the hydrolysis of the alk-1-enyl bond at the C-1 position of 1-alkenyl-2-acyl-sn-glycero-3-phosphoethanolamine (ethanolamine plasmalogens) in the ...hamster heart was examined. A new spectrophotometric assay was developed for this study, in which the aldehyde released by the hydrolysis of the plamalogenase was oxidized to carboxylic acid by the action of aldehyde dehydrogenase, with the production of the molar equivalent of NADH. The results obtained from the spectrophotometric assay were comparable to those obtained by determining the rate of ethanolamine plasmalogens utilized during the reaction. However, the sensitivity of the spectrophotometric assay for plasmalogenase was shown to be 25-fold higher than with the methods described previously and enzyme activity could be detected with 1 micrograms of microsomal protein. Hamster heart plasmalogenase activity was located exclusively in the microsomal fraction, and the enzyme displayed a pH optimum at 8.5. The enzyme showed no absolute requirement for divalent metallic cations.
The influence of L-cystein on the toxic and therapeutic responses of 4-(S-ethanol)-sulfido-cyclophosphamide (P1), a stabilized "activated" cyclophosphamide, was investigated. Stabilized "activated" ...cyclophosphamides hydrolyze under physiological conditions to 4-hydroxycyclophosphamide (4-OH-CP). The antitumor activity of P1 was investigated on a heterotransplanted human bladder sarcoma in nude mice and in perfusion experiments carried out on the isolated tumor bearing limb in rats. Due to its rapid hydrolysis to 4-OH-CP, P1 exhibits severe local toxicity which is decreased by the protector thiol L-cystein. Simultaneous application of double molar amounts of L-cystein reduces toxicity in nude mice to approximately one-third. Therapeutic activity is not affected by this ratio of L-cystein so that the protector thiol increases the therapeutic efficacy of P1. Higher amounts of L-cystein reduce both the acute toxicity in nude mice and the therapeutic efficacy against the human xenograft. The perfusion experiments demonstrate that a P1 concentration necessary to cure rats with tumor bearing limb is only tolerated in combination with L-cystein.
