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At least 19 recordsLinked to original sources
PubMed1986

Serum thiocyanate and smoking: interpretation of serum thiocyanate levels observed in a large health study.

In a Norwegian health study involving 25,300 persons the mean serum thiocyanate level in non-smokers was 33.9 mumol/l for males and 33.5 mumol/l for females. In moderate smokers (five to nine cigarettes per day) the mean level was 59.6 mumol/l for males and 70.9 mumol/l for females. In heavy smokers (greater than 25 cigarettes per day) the mean level was 87.3 mumol/l in males and 99.7 mumol/l in females. The difference between the thiocyanate levels in females and males smoking the same number of cigarettes can be explained by the sex difference in distribution volume for thiocyanate. Among non-smokers the mean level of serum thiocyanate was the same whether the persons had been indirectly exposed to tobacco smoke or not. The mean serum thiocyanate levels were up to 10 mumol/l higher in the last half part of the year than in the first part. This can be explained by seasonal variations in the content of thiocyanate in the diet. The range of the individual thiocyanate level was great both in non-smokers and in smokers, resulting in a large overlap. Serum thiocyanate can therefore not distinguish all non-smokers from all smokers. However, by choosing suitable 'cut-off levels' it is possible to extract from the total population groups consisting of a large majority of smokers and only a few non-smokers and vice versa.

Adult↗
PubMed1992

A thiocyanate hydrolase of Thiobacillus thioparus. A novel enzyme catalyzing the formation of carbonyl sulfide from thiocyanate.

A thiocyanate hydrolase that catalyzes the first step in thiocyanate degradation was purified to homogeneity from Thiobacillus thioparus, an obligate chemolithotrophic eubacterium metabolizing thiocyanate to sulfate as an energy source. The thiocyanate hydrolase was purified 52-fold by steps involving ammonium sulfate precipitation, DEAE-Sephacel column chromatography, and hydroxylapatite column chromatography. The enzyme hydrolyzed 1 mol of thiocyanate to form 1 mol of carbonyl sulfide and 1 mol of ammonia as follows: SCN- + 2H2O----COS + NH3 + OH-. This is the first report describing the hydrolysis of thiocyanate to carbonyl sulfide by an enzyme. The enzyme had a molecular mass of 126 kDa and was composed of three different subunits: alpha (19 kDa), beta (23 kDa), and gamma (32 kDa). The enzyme exhibited optimal activities at pH 7.5-8.0 and at temperatures ranging from 30 to 40 degrees C. The Km value for thiocyanate was approximately 11 mM. Immunoblot analysis with polyclonal antibodies against the purified enzyme suggested that it was induced in T. thioparus cells when the cells were grown with thiocyanate.

Blotting, Western↗
PubMed1995

Effect of magnetic field strength on the linewidth and spin-lattice relaxation time of the thiocyanate carbon of cyanylated beta-lactoglobulin B: optimization of the experimental parameters for observing thiocyanate carbons in proteins.

The linewidths and spin-lattice relaxation times of the 13C-n.m.r. signal at 109.7 p.p.m. due to the thiocyanate carbon of intact [cyanato-13C]cyanylated-beta-lactoglobulin-B have been determined at magnetic field strengths of 1.88, 6.34 and 11.74 T as well as the spin-lattice relaxation times of its backbone alpha-carbon atoms. The linewidths were directly proportional to the square of the magnetic field strength and we conclude that, at magnetic field strengths of 6.34 T or above, more than 70% of the linewidth will be determined by chemical-shift anisotropy. We estimate that the spin-lattice relaxation time resulting from the chemical-shift anisotropy of the thiocyanate carbon is 1.52 +/- 0.1 s and we conclude that for magnetic field strengths of 6.34 T and above the observed spin-lattice relaxation time of the thiocyanate carbon will be essentially independent of magnetic field strength. Using the rigid-rotor model we obtain estimates of the rotational correlation time of [cyanato-13C]cyanylated-beta-lactoglobulin-B and of the chemical-shift anisotropy shielding tensor of its thiocyanate carbon. We have calculated the linewidths and spin-lattice relaxation times of thiocyanate carbons at magnetic field strengths of 1.88-14.1 T in proteins with M(r) values in the range 10,000-400,000. The effects of magnetic field strength on the resolution and signal-to-noise ratios of the signals due to thiocyanate carbons attached to proteins of M(r) greater than 10,000 are discussed.

Carbon↗
PubMed1988

Determination of oxidizable inorganic anions by high-performance liquid chromatography with fluorescence detection and application to the determination of salivary nitrite and thiocyanate and serum thiocyanate.

A sensitive method for the simultaneous determination of oxidizable inorganic anions (sulphide, thiocyanate, thiosulphate and nitrite) was developed by use of high-performance liquid chromatography and fluorimetric detection based on the formation of fluorescent cerium(III) by a redox reaction with cerium(IV). The detection limits are 0.1 nmol for both thiocyanate and nitrite, 0.3 nmol for thiosulphate and 0.8 nmol for sulphide per 10-microliters injection volume. This system can be utilized for the determination of salivary thiocyanate and nitrite and serum thiocyanate.

Anions↗
PubMed1966

The inhibition of streptococci by lactoperoxidase, thiocyanate and hydrogen peroxide. The oxidation of thiocyanate and the nature of the inhibitory compound.

1. The products of the lactoperoxidase-catalysed oxidation of thiocyanate by hydrogen peroxide were sulphate, carbon dioxide and ammonia. Cyanate, sulphite and a compound showing increased extinction at 235mmu (the ;235 compound') were intermediate oxidation products. 2. Two of the intermediates acted as electron acceptors in the oxidation of NADH(2). Thus NADH(2) was oxidized by sulphite in the presence of lactoperoxidase (EC 1.11.1.7) and Mn(2+) and by the ;235 compound' in the presence of an enzyme, the NADH(2)-oxidizing enzyme, present in extracts of lactoperoxidase-resistant streptococci. Sulphur dicyanide also acted as an electron acceptor in the latter reaction. The ;235 compound' was also reduced non-enzymically by sulphite. 3. The glycolysis of lactoperoxidasesensitive streptococci suspended in glucose solution was not inhibited by sulphite, cyanate, cyanide or the ;235 compound' but was inhibited by sulphur dicyanide. The inhibition by 0.1mm-sulphur dicyanide could be reversed, as could that caused by lactoperoxidase, thiocyanate and hydrogen peroxide, by washing the cells or by the addition of a cell-free extract of a lactoperoxidase-resistant streptococcus. 4. The effects of 0.1mm-sulphur dicyanide on catabolic enzymes of resting streptococci were very similar to those of the lactoperoxidase-thiocyanate-hydrogen peroxide system. Thus hexokinase was completedly inhibited, glucose 6-phosphate dehydrogenase and aldolase were partially inhibited and phosphohexokinase was little affected in both cases.

Autoradiography↗
PubMed1991

Spectrophotometric flow injection determination of trace amounts of thiocyanate based on its reaction with 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol and dichromate: assay of the thiocyanate level in saliva from smokers and non-smokers.

A simple and very sensitive spectrophotometric flow injection (FI) procedure for the determination of trace amounts of thiocyanate is described. The proposed method is based on the reaction between thiocyanate and 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol, which, in 2 mol dm-3 acidic media in the presence of a strong oxidizing agent, produces an intensely coloured product. Several oxidants are potentially applicable, but it is shown that dichromate is preferable. As the reaction product formed is unstable and the signal inherently is recorded on a high background level, it is demonstrated that FI constitutes an ideal method in order to monitor reproducibly and repeatedly the kinetically transient signal that is obtained. Based on optimization by a factorial experimental design, the detection limit of the procedure was found to be 3.5 mumol dm-3, and the standard deviation between samples was 0.16 mumol dm-3. No significant interferences were observed; a 1000-fold excess of cyanide could readily be tolerated within the experimental error. With a sample volume of 50 microliters being injected, the sampling frequency was 60 samples h-1. The system was tested with saliva samples from non-smokers and smokers, and the results show that it is possible to distinguish between these two categories of individuals. As an added benefit, the detection limit of the analytical procedure allows the samples to be diluted 100-fold, so that centrifugation for 5 min is the only preliminary sample preparation that is necessary.

Azo Compounds↗
PubMed1997

Low catalytic turnover of horseradish peroxidase in thiocyanate oxidation. Evidence for concurrent inactivation by cyanide generated through one-electron oxidation of thiocyanate.

The catalytic turnover of horseradish peroxidase (HRP) to oxidize SCN- is a hundredfold lower than that of lactoperoxidase (LPO) at optimum pH. While studying the mechanism, HRP was found to be reversibly inactivated following pseudo-first order kinetics with a second order rate constant of 400 M-1 min-1 when incubated with SCN- and H2O2. The slow rate of SCN- oxidation is increased severalfold in the presence of free radical traps, 5-5-dimethyl-1-pyrroline N-oxide or alpha-phenyl-tert-butylnitrone, suggesting the plausible role of free radical or radical-derived product in the inactivation. Spectral studies indicate that SCN- at a lower concentrations slowly reduces compound II to native state by one-electron transfer as evidenced by a time-dependent spectral shift from 418 to 402 nm through an isosbestic point at 408 nm. In the presence of higher concentrations of SCN-, a new stable Soret peak appears at 421 nm with a visible peak at 540 nm, which are the characteristics of the inactivated enzyme. The one-electron oxidation product of SCN- was identified by electron spin resonance spectroscopy as 5-5-dimethyl-1-pyrroline N-oxide adduct of the sulfur-centered thiocyanate radical (aN = 15.0 G and abetaH = 16.5 G). The inactivation of the enzyme in the presence of SCN- and H2O2 is prevented by electron donors such as iodide or guaiacol. Binding studies indicate that both iodide and guaiacol compete with SCN- for binding at or near the SCN- binding site and thus prevent inactivation. The spectral characteristics of the inactivated enzyme are exactly similar to those of the native HRP-CN- complex. Quantitative measurements indicate that HRP produces a 10-fold higher amount of CN- than LPO when incubated with SCN- and H2O2. As HRP has higher affinity for CN- than LPO, it is concurrently inactivated by CN- formed during SCN- oxidation, which is not observed in case of LPO. This study further reveals that HRP catalyzes SCN- oxidation by two one-electron transfers with the intermediate formation of thiocyanate radicals. The radicals dimerize to form thiocyanogen, (SCN)2, which is hydrolyzed to form CN-. As LPO forms OSCN- as the major stable oxidation product through a two-electron transfer mechanism, it is not significantly inactivated by CN- formed in a small quantity.

Binding Sites↗
PubMed1986

Mechanism of gastric antisecretory effect of thiocyanate: further evidence for the thiocyanate-induced impediment in gastric H+,K+-ATPase function.

Two hypotheses have recently been proposed for the thiocyanate inhibition of gastric acid secretion--a protonophore mechanism and an uncoupling model. The mechanistic aspects for the latter scheme have been examined on the following basis: capability of generating verifiable predictions, supporting evidence that is unambiguous, and compatibility with experimental realities. Gastric microsomes bind 5 nmol of SCN-/mg, and a "pure" and highly active fraction of H+,K+-ATPase prepared from gastric microsomes binds about 15 nmol of SCN-/mg. The affinity of SCN- binding to gastric microsomes changes from 10 to 25 mM in the presence of 20 mM K+ suggesting competition between K+ and SCN-. Potassium also displaces the bound SCN- from "pure" H+,K+-ATPase with a Ki of about 25 mM. Of the cations tested--Tl+, K+, Rb+, Cs+, NH4+, Na+, and Li+--Tl+ was the most effective in displacing bound SCN- while Na+ and Li+ were without effect. The effects of anions such as Cl-, NO3-, and gluconate were found to be nonspecific and absolutely dependent on K+ as cocation. Sulfate and OCN-, on the other hand, showed an ability to displace SCN- as both K+ and Na+ salts. For SO4(-2) the K+ form was much more effective than the Na+ salt. Besides these antagonistic effects of K+ and congeners with the H+,K+-ATPase-bound SCN-, a competition between K+ and SCN- was also observed at the level of gastric K+-stimulated pNPPase reaction. The effects of SCN- and two other unrelated anions, F- and NO2-, on artificial delta pH across the microsomal vesicles exhibited a lack of appreciable change up to 5 mM and a small (about 13%) reduction between 10 and 20 mM. However, a combination of CCCP and nigericin or valinomycin completely abolished the delta pH under identical conditions. The present data in conjunction with other reports suggest that the proton impediment model best explains the gastric antisecretory effects of SCN-.

4-Nitrophenylphosphatase↗