General synthesis of 3-substituted alkenyl GABA as potential anticonvulsants.

Stereospecific synthesis of cis and trans 3-substituted vinyl-gamma-aminobutyric acid analogs were obtained by either a Claisen rearrangement or a Wittig reaction from common diene precursors.

Cure of Trypanosoma brucei brucei and Trypanosoma brucei rhodesiense infections in mice with an irreversible inhibitor of S-adenosylmethionine decarboxylase.

A structural analog, 5'-([(Z)-4-amino-2-butenyl]methylamino)-5'-deoxy adenosine (MDL 73811), of decarboxy S-adenosyl-L-methionine, the product of the reaction catalyzed by S-adenosyl-L-methionine (AdoMet) decarboxylase (DC), was found to inhibit Trypanosoma brucei brucei AdoMet DC. The inhibition was time dependent (tau 50, 0.3 min), exhibited pseudo-first-order kinetics (Ki, 1.5 microM), and was apparently irreversible. The natural substrate of the reaction, AdoMet, protected the enzyme from inactivation, suggesting that MDL 73811 was directed at the enzyme active site and was probably catalytically activated. Administration of MDL 73811 to T. b. brucei-infected rats resulted in rapid inhibition of AdoMet DC activity, a decrease in spermidine, and an increase in putrescine in the trypanosomes isolated from treated rats. Treatment of T. b. brucei-infected mice with MDL 73811 (20 mg/kg of body weight intraperitoneally twice daily for 4 days) resulted in cures of the trypanosome infections. Additionally, drug-resistant T. brucei rhodesiense infections in mice were cured by either a combination of MDL 73811 (50 mg/kg intraperitoneally three times per day for 5 days) and relatively low oral doses of alpha-difluoromethylornithine or MDL 73811 (50 mg/kg per day for 7 days) administered alone in implanted miniosmotic pumps. These data suggest that MDL 73811 and, perhaps, other inhibitors of AdoMet DC have potential for therapeutic use in various forms of African trypanosomiasis.

Catalytic irreversible inhibition of bacterial and plant arginine decarboxylase activities by novel substrate and product analogues.

Arginine decarboxylase (ADC) activity from Escherichia coli and two plant species (oats and barley) was inhibited by five new substrate (arginine) and product (agmatine) analogues. The five compounds, (E)-alpha-monofluoromethyldehydroarginine (delta-MFMA), alpha-monofluoromethylarginine (MFMA), alpha-monofluoromethylagatine (FMA), alpha-ethynylagmatine (EA) and alpha-allenylagmatine (AA), were all more potent inhibitors of ADC activity than was alpha-difluoromethylarginine (DFMA), the only irreversible inhibitor of this enzyme described previously. The inhibition caused by the five compounds was apparently enzyme-activated and irreversible, since the loss of enzyme activity followed pseudo-first-order kinetics, was time-dependent, the natural substrate of ADC (arginine) blocked the effects of the inhibitors, and the inhibition remained after chromatography of inhibited ADC on Sephadex G-25 or on overnight dialysis of the enzyme. DFMA, FMA, delta-MFMA and MFMA were effective at very low concentrations (10 nM-10 microM) at inhibiting ADC activity in growing E. coli. FMA was also shown to deplete putrescine effectively in E. coli, particularly when combined with an inhibitor of ornithine decarboxylase, alpha-monofluoromethyl-putrescine. The potential uses of the compounds for the study of the role of polyamine biosynthesis in bacteria and plants is discussed.