The inhibition of urease and proteases by sodium saccharin

Sodium saccharin, at concentrations similar to those in the urine of rats fed 1-5% sodium saccharin in their diet, markedly inhibited urease, and 3 proteases in vitro and sodium ion did not appear to play a role in enzyme inhibition. These observations suggest that enzyme inhibition of any of a large number of enzymes may play a role in the tumorigenesis of the urinary bladder by saccharin.

Therapy for urolithiasis with hydroxamic acids. IV. Prevention of infected urinary stone formation with N-(pivaloyl)glycinohydroxamic acid

With the aim of finding a prospective therapeutic compound with a promising potential for the treatment of urolithiasis, we evaluated the effectiveness of a new potent inhibitor of urease, N-(pivaloyl)glycinohydroxamic acid. The present study revealed that N-(pivaloyl)glycinohydroxamic acid effectively inhibited the alkalinization of urine and the stone formation in vitro and in vivo, due to its strong inhibitory potency against the ureolytic activity of intact Proteus mirabilis. The possibility of the clinical application of this compound in the prevention of struvite stone formation caused by infection of urea-splitting bacteria awaits evaluation of the safety of this compound.

Effect of acetohydroxamic acid on rumen urease activity in vitro

Acetohydroxamic acid at a concentration of 1 X 10(-6) M, 6 X 10(-5) M, and 1 X 10(-3) M inhibited urease of intact rumen microbes in vitro by 11%, 50%, and 74%. Inhibition of rumen urease by the acid reached equilibrium state, unlike jack bean urease. Inhibition was maximum over a broad range of pH (8 to 10) and it did not resemble the pH activity profile of rumen urease. Sulfhydryl compounds did not reverse the inhibition; however, addition of these compounds prior to acetohydroxamic acid addition prevented inhibition. The nature of inhibition was noncompetitive with inhibitor constant 4.8 X 10(-5) M. Acetohydroxamic acid at a concentration that produced 50% urease inhibition did not affect rumen cellulase and proteolytic enzymes in vitro. The complex of acetohydroxamic acid-rumen urease is dissociable on dialysis.

Separation and biologic activities of individual components of S15-1, a streptothricin class antibiotic

A method is described for isolation of gram quantities of the components of the streptothricin complex S15-1 utilizing CM Sephadex column chromatography eluted with 10% acetic acid as an eluant followed by gradient elution with 10% acetic acid containing 0.02 N approximately 0.03 N HCI. Streptothricins F and E, as well as an unidentified component C1, have been isolated and their comparative biological activities determined. Streptothricins F and E were comparable in taeniacidal activity in mice infected with Hymenolepis nana ia feeding either one at 0.05% in the diet removed 92 approximately 100% of the adult tapeworms. The unidentified component C1 was inactive at the levels tested. In contrast, component C1 was the most active in antimicrobial activity against Bacillus subtilis and in inhibiting the urease activity of proteus mirabilis. In the former test, the ratios of activity were; 1:7:30 for F:E:C1 and in the latter; 1:2:4 for F:E:C1.

[Studies on the effect of phosphoric phenyl ester diamide as inhibitor of the rumen urease of dairy cows. 1. Influence on urea hydrolysis, ammonia release and fermentation in the rumen]

An amount of 0, 0.1, 0.5 and 1.0% (related to N) of phosphoric phenyl ester diamide (PPD) effective as urease blocking substance was applied to the surface of urea with oilbitumen and fed to cows with rumen cannulae over a period of 31 resp. 164 ... 167 days. (The ration essentially consisted of 4.5 kg dried roughage and 1.5 kg starch or 1.1 kg starch plus 0.4 kg sugar and contained 50 g urea). By treating the urea with PPD, the activity of urease, the hydrolysis rate of urea and the NH3-concentration in the rumen were significantly diminished 0.5 to 2 hours after feeding (alpha = 0.05). The effect of PPD was greatest in the first days and decreased with the advancing feeding period. In the variant with 0.5% PPD the examined parameters were significantly reduced after 142 to 164 days, too. This effect remained traceable in its diminished form even after the preparation was discontinued over a period of 35 days. The dynamics of the NH3-concentration was not altered by PPD after a longer feeding period. One can conclude that PPD inhibits the hydrolysis of urea but does not retard it. In conclusion one can say that, because of PPD, the toxicity of urea is lower without the utilisation of urea being better. Due to PPD the molar propionate level in volatile fatty acids decreases significantly and the acetate-propionate relation is expanded.

[Studies on the effect of phosphoric phenyl ester diamide as inhibitor of the rumen urease of dairy cows. 2. The metabolism of 15N-urea]

Two lactating dairy cows supplied with rumen and duodenal re-entrance cannulae received with their rations containing 8.2% vegetable crude protein 180 g urea per day (I) or urea treated with the urease inhibitor phosphoric phenyl ester diamide (PPD, 1% of the N-quota). The cows, accustomed to urea, received the PPD-urea without adaptation (II) and after a 30-day adaptation (III) to PPD. On the first day of the experiment one half of the urea was given ruminally in its 15N-labelled form. 2 h after the isotope supplementation 62.5 and 24 mg NH3 and 6.58 and 21 mg urea/100 ml could be detected in the rumen juice of I to III. Within 72 h 16.6, 26.1 and 25.2% of the 15N-excess given (15N') passed the duodenum in TCA - soluble form and 31.2, 28.4 and 41.7% in TCA - precipitable form. 15.6, 24.4 and 21.5% of the total amount of 15N were excreted in urine and 4.5, 4.6 and 6.0% in the milk protein. The values for faeces were 14.4, 14,4 and 15.4%. The conclusion from these results and from the dynamics of the relative 15N' in the fractions of the rumen fluid is that with a limited inhibition of rumen urease by PPD as it develops after the adaptation, the utilisation of urea-N can be improved.

Jack bean urease (EC 3.5.1.5). IV. The molecular size and the mechanism of inhibition by hydroxamic acids. Spectrophotometric titration of enzymes with reversible inhibitors

Kinetic, spectral, and other studies establish that hydroxamic acids bind reversibly to active-site nickel ion in jack bean urease. Equilibrium ultracentrifugation studies establish that the molecular weight of native urease is 590 000 +/- 30 000 while that of the subunit formed in 6 M guanidinium chloride in the presence of beta-mercaptoethanol is approximately 95 000. Essentially the same subunit molecular weight (approximately 93 000) is found by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate, subsequent to denaturation in a guanidinium chloride - beta-mercaptoethanol system at various temperatures. Coupled with an equivalent weight of 96 600 for binding of the inhibitors acetohydroxamic acid and phosphoramidate, these results establish securely that urease is a hexamer with one active site per 96 600-dalton subunit. Consistent values for the equivalent weight are obtained by a routine spectrophotometric titration of the active site of freshly prepared urease with trans-cinnamoylhydroxamic acid. General equations are derived which describe spectrophotometric titrations of binding sites of any enzyme with a reversible inhibitor. These equations allow the evaluation of the difference spectrum of the protein-inhibitor complex even when the binding sites cannot readily be saturated with the inhibitor or vice versa.

Therapy for urolithiasis by hydroxamic acids. III. Urease inhibitory potency and urinary excretion rate of N-acylglycinohydroxamic acids

Hydroxamic acid, a potent urease inhibitor, having a high urinary excretion rate is expected to be a therapeutic agent for urolithiasis caused by urea-splitting bacterial infection of the urinary tract. Twenty-one new derivatives of N-aliphatic-acylglycinohydroxamic acids (GHAs) were synthesized, and their inhibitory potencies against the urease activity of sword bean in a phosphate buffer and against the ureolytic activity of Proteus mirabilis in human urine, and their urinary excretion rates in rats were also measured for this purpose I50 values of most of GHAs against the urease activity of sword bean were about 1 to 10 microM and 2-ethyl-n-butyroyl GHA was the most potent inhibitor with the value of 0.79 microM. I50 values of most of the GHAs against the ureolytic activity of Proteus mirabilis were about 5 to 50 microM and n-nonaroyl GHA was the most potent inhibitor with the value of 3.6 microM. 2,2-Dimethylpropionyl GHA had the highest urinary excretion rate with the recovery of 11%. Routes of administration of 2,2-dimethylpropionyl GHA and sex of rats used did not affect the amount of urinary excretion at all. The results in this report suggest that DL 2-methyl-n-butyroyl, 2-ethyl-n-butyroyl and 2,2-dimethylpropionyl GHA are the most hopeful therapeutic agents for urolithiasis among them.

Prevention of infected urinary stones in rats by urease inhibitor: a new hydroxamic acid derivative

We tested the inhibitory power and urinary excretion of several derivatives of hippurohydroxamic acid, including some newly synthesized compounds. m-Methoxyhippurohydroxamic acid (UCD II) strongly inhibited urease activity and high urinary excretion after oral administration to rats. UCD II inhibited the alkalinization of infected urine in vitro and in vivo and prevented bladder stone formation when it was orally administered to rats with urinary tract infection caused by Proteus mirabilis. The clinical application of UCD II to the prevention of pathologic sequelae of urinary infection with urease-producing bacteria awaits evaluation of the safety of the compound.

Therapy for urolithiasis by hydroxamic acids. II. Urease inhibitory potency and urinary excretion rate of hippurohydroxamic acid derivatives

The apparent I50 values of various hippurohydroxamic acids against urease activity of sword bean were mostly 0.5 to 2.0 microM regardless of hydrophobicity of their substituents. However, the marked increase of hydrophilicity caused by substitution of trimethoxy groups conspicuously decreased the inhibitory potency. Methylation at alpha-position of the hydroxamic acid group in these compounds remarkably decreased the inhibitory potency, probably owing to steric hindrance by the alpha-methyl group. Thenoyl-, furoyl- and nicotino-glycinohydroxamic acids which are bioisostereomers of hippurohydroxamic acid had I50 values of 0.64, 1.3 and 5.3 microM, respectively. Furthermore, the inhibitory potency of some substituted hippurohydroxamic acids against the ureolytic activity of intact Proteus mirabilis isolated from patients with urinary tract infection, were half to one-tenth of those against urease activity of sword bean. On the other hand, m- and p-nitro-, m- and p-methoxy-, m- and p-acetylamino-hippurohydroxamic acid and furoylglycinohydroxamic acid showed high urinary excretion rates of 14 to 16% of the doses administered orally to rats, while most of the others had excretion rates of about 3 to 5%.

Quantitative structure-activity relationships between hydroxamic acids and their urease inhibitory potency

Quantitative structure activity relationships between physico-chemical properties of four series of more than sixty hydroxamic acids [R-(CONHCH2)n-CONHOH, R=aromatic or aliphatic, n=1 or 0) and their urease inhibitory activities were examined. The best improved regression equation primarily indicated that the inhibitory activities of hydroxamic acids were parabolically varied with the hydrophobic variable, pi of the R moiety and the optimal pi value was calculated to be 2.58. Furthermore, the inhibitory activities of congeners were found to be significantly affected by the B1 variable representing the minimum width of steric size of the R moiety. Besides, it was clarified by using two indicator variables that inhibitory activities were not affected by the R moiety, whether aromatic or aliphatic, but positively affected by the presence of the -CONHCH2-group between the R moiety and the hydroxamic acid group.

The effect of acetohydroxamic acid on the induction of bacterial ureases

The ureases of Proteus mirabilis, Proteus vulgaris, and Proteus rettgeri are inducible by urea. Induction is increased when both urea and acetohydroxamic acid, an inhibitor of urease, are present during bacterial growth. Acetohydroxamic acid alone does not cause induction, but, by preventing the hydrolysis of urea, it minimizes pH increases and allows induction to occur much more effectively. The ureases of Proteus morganii and other bacterial genera are not inducible by this method. The relevance of our findings to the formation and management of infection stones is discussed.

Jack bean urease (EC 3.5.1.5). III. The involvement of active-site nickel ion in inhibition by beta-mercaptoethanol, phosphoramidate, and fluoride

Interaction of beta-mercaptoethanol with urease produces large, rapid and fully reversible spectral changes in that part of the electronic absorption spectrum which is associated with the tightly bound nickel ions. The spectrophotometrically determined value of the dissociation constant of the beta-mercaptoethanol-urease complex (0.9 +/- 0.05 mM at pH 7.12 and 25 degrees C) is in agreement with the Ki (0.72 +/- 0.26 mM) for beta-mercaptoethanol acting as a competitive inhibitor in the hydrolysis of urea. This constitutes direct evidence that the nickel in jack bean urease is at the active site. Inhibition of urease by phosphoramidate is slowly achieved and slowly reversed, and upon reactivation of the isolated phosphoramidate-urease complex, phosphoramidate is regenerated in good yield. Spectrophotometric experiments indicate that phosphoramidate binds to nickel ion in urease. Competition with beta-mercaptoethanol was used to determine a dissociation constant (1.23 +/- 0.10 mM at pH 7.12 and 25 degrees C) for a fluoride-evidence is presented which indicates that in the presence of urea, a ternary complex (fluoride-urea-urease) is formed.

Jack been urease (EC 3.5.1.5). II. The relationship between nickel, enzymatic activity, and the "abnormal" ultraviolet spectrum. The nickel content of jack beans

At low pH, EDTA promotes the loss of the tightly bound nickel ions from jack bean urease. The specific activity of soluble enzyme after partial EDTA-promoted inactivation is a linear function of the nickel content. The results are consistent with the presence of 2.0 nickel ions per 97 000-dalton subunit in pure urease. The time scale for loss of enzymatic activity and nickel under these conditions is similar to that for loss of the "abnormal" tail absorption in the ultraviolet and visible absorption spectrum of urease (including the shoulder at approximately 420 nm). This indicates that nickel in urease is essential for enzymatic activity and establishes that the metal ions are in part responsible for the tail absorption in the ultraviolet spectrum of urease. After partial inactivation in the presence of EDTA either at low pH or in 2.5 M guanidinium chloride at neutral pH, urease did not regain activity in the presence of Ni2+. As yet apourease has not been produced reversibly. Jack bean seeds grown hydroponically without added nickel were low in both urease activity and nickel (10 and 6%, respectively, of parent seeds). Several other metal ions were readily available. This result suggests that metal ions other than nickel cannot substitute for nickel in the formation of normally active urease.

An enzyme-immobilization procedure for the analysis of enzyme-inhibiting chemicals in water

The enzymes cholinesterase and urease were mixed individually with gelatin and immobilized onto the inside surface of glass capillary tubes. After the gelatin-enzyme mixture had dried, water samples containing various enzyme inhibiting test chemicals were pumped through the tubes to enable interaction to proceed between the foreign agents and the enzymes. Substrate for each enzyme was later passed through the tubes and any differences in relative enzyme activity determined. This procedure may be useful for health and environmental studies, particularly in the rapid testing for micro- and nanomolar quantities of enzyme-inhibiting pollutants in natural waters and complex effluents.

Rapid screening for urease inhibitors

Two methods are described that are suitable for the rapid screening of compounds as urease inhibitors. The first utilizes an electrode sensitive to NH4+ ions; the second is dependent on pH rise. A feature of both is a direct readout of reaction rate.