Taiji Inui

ACTIVATION OF MITOMYCIN C AND QUINONE DRUG METABOLISM BY NADPH-CYTOCHROME P-450 REDUCTASE

Microsomal NADPH-cytochrome P-450 reductase (EC 1.6.2.4) and xanthine oxidase (EC 1.2.3.2) catalyzed the activation of antitumor antibiotic, mitomycin C, under anaerobic conditions. Under aerobic conditions, NADPH-cytochrome P-450 reductase catalyzed the quinone structure containing antitumor compound-dependent NADPH oxidation. With our previous results, the direct contribution of NADPH-cytochrome P-450 reductase to the quinone drug metabolism was generalized.

Interaction of new anthracycline antibiotics with DNA. Effects on nucleic acid synthesis and binding to DNA

The effects of various new anthracycline antibiotics on DNA and RNA synthesis were studied using DNA polymerase I (EC 2.7.7.7), RNA polymerase (EC 2.7.7.6) obtained from Escherichia coli and reverse transcriptase obtained from avian myeloblastosis virus. Aclacinomycin A, its analogues, baumycins A1 and A2, adriamycin and daunomycin showed potent inhibitory effects on these polymerases, with calf thymus DNA as template, with IC50 values of 10-30 microM. With poly(rA) x d(pT)10 as template for reverse transcriptase, aclacinomycin A and daunomycin showed IC50 values higher than 500 microM. Baumycins B1, B2, C1, and C2 showed high IC50 values on three polymerases. Addition of excess template DNA to the reaction mixture reversed the inhibitory effect of anthracyclines. Addition of calf thymus DNA to anthracyclines caused a bathochromic and hypochromic change in the visible spectrum. Apparent binding constant for aclacinomycin A, its analogues, and adriamycin were in the range of (1-2) X 10(6) M-1. Aclacinomycin A and adriamycin also bind to heat denatured DNA, but not strongly to yeast RNA. From these results, the structure-activity relationships of new anthracyclines on DNA binding and polymerase reactions are discussed.

Effect of guanosine 5?-diphosphate 3?-diphosphate and related nucleoside polyphosphates on induction of tryptophanase and ?-galactosidase in permeabilized cells of Escherichia coli

Exogenous addition of guanosine and adenosine 5′-(mono, di and tri) phosphate 3′-diphosphates (pppGpp, ppGpp, pGpp, pppApp, ppApp and pApp) stimulated the synthesis of tryptophanase and β-galactosidase in permeabilized cells of Escherichia coli. From the results obtained with ppGpp and pppApp, this effect appeared to be at a transcriptional level and depended greatly on the growth condition; the largest effect was observed in cells under shiftdown or grown on poor energy source. ppGpp and pppApp, unlike cyclic AMP, did not act to overcome the inhibition of enzyme induction by glucose, but in combination with cyclic AMP caused a synergistic stimulation effect. In the shiftdown cells, ppGpp and pppApp gave 30% or more stimulation effect on tryptophanase induction while cyclic AMP did not stimulate induction. There was therefore a pronounced difference between cyclic AMP and ppGpp or pppApp in stimulatory function.

NADH-dependent cinerulose reductase in rat liver microsomes

Abstract In the course of studies on the metabolism of a new antitumor anthracycline antibiotic, aclacinomycin A, the new keto reductase which catalyzes the reduction of keto group of L-cinerulose of aclacinomycin A to L-rhodinose was found in rat liver microsomal membrane. The enzyme requires NADH for the reduction and showed optimum pH at 7.0. Km value for aclacinomycin A, 2.1 × 10−5 M and the concentration of NADH need to half maximal activity, 6.2 × 10−5 M were obtained. The activity was potently inhibited by detergents, such as Triton X-100, sodium deoxycholate and sodium dodecyl sulfate.

Effect of adenosine-5′-triphosphate-3′-diphosphate and related nucleoside polyphosphates on the spore germination of Streptomyces galilaeus

Exogenous addition of adenosine- and guanosine 5′-(di- and tri) phosphate 3′-diphosphate (pppApp, ppApp, pppGpp and ppGpp) at the concentration of 0.5 mM inhibits spore germination of Streptomyces galilaeus ATCC 31133. This reversible inhibitory effect appeared to be at the transcriptional level, and also depends on the phase of spore germination; pppApp inhibited more strongly RNA synthesis in the period of the germ tube emergence than the early stage of germination. No inhibitory effect was observed with normal purine and pyrimidine nucleosides, nucleotides, pApp, pGpp, cyclic AMP and pyrophosphoric acid at the concentration of 0.1–1.0 mM.