Jacob Yashphe

The antimicrobial activity of the essential oil from Achillea fragrantissima

Essential oil from Achillea fragrantissima exerted a bactericidic effect on several gram positive and gram negative bacterial strains, as well as on Candida albicans. The oil was fractionated on sillica gel columns by a gradient of ether in petrol ether (30 degrees C-40 degrees C). Two fractions which contained less polar compounds were active against C. albicans only. The fractions which contained more polar compounds inhibited the growth of all the microorganisms tested. One of these compounds was identified as terpinen-4-ol. Commercial terpinen-4-ol had a similar antimicrobial activity.

The Antibacterial and Antispasmodic Activity of Artemisia herba alba Asso. II. Examination of Essential Oils from Various Chemotypes

AbstractThe essential oils from four Artemisia herba alba populations collected in Israel were investigated for their antibacterial and antispasmodic activities. All the oils had slight antibacterial activities in the concentration range of 1-2 mg/ml. Some correlations between the chemical composition of the oils and their antibacterial activity was observed. All the essential oils tested showed marked antispasmodic effects on rabbit jejunum at about 1 × 10−5%. The antibacterial together with the antispasmodic effects may explain the extensive use of A. herba alba in folk medicine.

Purification and characterization of uridine and thymidine phosphorylase from Lactobacillus casei

Uridine and thymidine phosphorylases have been purified to homogeneity from crude extracts of Lactobacillus casei. Both enzymes had an apparent molecular mass of about 80 kDa. Uridine phosphorylase consisted of four identical subunits while thymidine phosphorylase was composed of two identical ones. The sequence of 23 amino-acid residues from its N-terminal end was analyzed. Uridine phosphorylase had a Km of 5.0 x 10(-3) M for uridine and 1.24 x 10(-1) M for phosphate, while thymidine phosphorylase had a Km of 1.32 x 10(-1) M for thymidine and 1.0 x 10(-1) M for phosphate. Uridine phosphorylase was equally active with uridine and 5-methyluridine, but had a low activity towards thymidine. Its activity was inhibited competitively by 3-O-methyl-alpha D-glucopyranoside, on the other hand thymidine phosphorylase activity was not affected by this compound. Thymidine phosphorylase showed specificity towards the deoxyribosyl moiety of the substrate. In addition, it required a nonsubstituted pyrimidine moiety or one which was substituted in position 5. The pattern of the double-reciprocal plots of the initial velocities vs. the concentrations of either one of the substrates, and the product inhibition kinetics, indicated that the catalytic mechanism of both enzymatic reactions is sequential rather than Ping-Pong and that the sequence of the addition of the substrates is random (rapid equilibrium). In the case of the uridine phosphorylase-catalyzed reaction, the products are also released randomly, while in the thymidine phosphorylase-catalyzed reaction deoxyribose 1-phosphate is released after thymine.

Mutations affecting uridine monophosphate pyrophosphorylase or the argR gene in Escherichia coli. Effects on carbamoyl phosphate and pyrimidine biosynthesis and on uracil uptake.

SummaryIn the course of experiments directed towards the isolation of mutants of Escherichia coli K12 with altered regulation of the synthesis of carbamoylphosphate synthetase, two types of mutations were found to affect the cumulative repression of this enzyme by arginine and uracil. Alteraction of the arginine pathway regulatory gene, argR, was shown to reduce the repressibility of the enzyme by both end products while mutations affecting uridine monophosphate pyrophosphorylase (upp) besides affecting uracil uptake preclude enzyme repression by uracil or cytosine in the biosynthesis of carbamoylphosphate and the pyrimidines. The upp mutations were located on the chromosome near the gua operon. Mutations previously designated as uraP are shown to belong to this class.The relation that could exist between the loss of uridine monophosphate pyrophosphorylase and the impairment of uracil uptake is discussed.A new method for isolating argR mutants in arginine-less strains is described.

Phosphatases ofAcinetobacter lwoffi. Localization and regulation of synthesis by orthophosphate

Several phosphomonoesterases and diesterases with various pH optima have been observed inAcinetobacter lwofi JW11. The osmotic shock fluids contained only those with an alkaline pH optimum. The synthesis of these phosphatases was regulated by external Pi concentrations. The shock fluids were fractionated by chromatography, yielding three fractions, two of which had hydrophobic properties. One of these contained an alkaline phosphatase that specifically required Ca2+ for activity. The diesterases required various divalent cations for their function. Mutants that lack phosphomonoesterase or both phosphomonoesterase and phosphodiesterase activities were isolated.

Effect of the essential oil fromAchillea fragrantissima onEscherichia coli cells

Escherichia coli cells treated with the essential oil from the plantAchillea fragrantissima released five polypeptides as well as K+ ions into the incubation medium. The oil also inhibited the respiration ofE. coli cells and reduced their ATP content. Electron micrographs showed that oil-treated cells were permeable to uranyl acetate. The effect of the essential oil on the cell membrane is discussed.

Estimation of micro amounts of carbamyl phosphate

Abstract A simple, fast and sensitive colorimetric method for the assay of carbamyl phosphate is described.

Estimation of micro amounts of urea and carbamyl derivatives.

Abstract A sensitive, fast and reproducible colorimetric method for the assay of micro amounts of urea and of some carbamyl derivatives is described.

The loss of Meso-tartrate dehydratase activity from induced cells of pseudomonads

1. 1.|Meso-tartrate-grown pseudomonads rapidly lost the induced enzyme, meso-tartrate dehydratase, in the absence of the inducer. The rate of enzyme loss was similar in washed cells resuspended without a carbon source and in cells continuing to grow in succinate or glucose media. Azide or dinitrophenol did not affect the rate of enzyme disappearance. The level of another inducible enzyme, histidine ammonialyase, did not drop under these conditions. 2. 2.|Enzyme destruction in whole cells was markedly dependent on temperature, being 7% per 30 min at 25° and almost 10 times as fast at 37°. Temperatures of 25° or higher also inactivated the enzyme in extracts. In extracts, addition of tartrate isomers or incubation under N2 stabilized the dehydratase, whereas glucose or succinate had no effect. These findings could be most readily explained by assuming that meso-tartrade dehydratase is a heat-sensitive protein which can be protected against denaturation in vivo by the inducer and its analogues or by incubation under N2.