Evidence for the existence of rhodanese (thiosulfate:cyanide sulfurtransferase) in plants: preliminary characterization of two rhodanese cDNAs from Arabidopsis thaliana

The existence of rhodanese (thiosulfate:cyanide sulfurtransferase; EC 2.8.1.1) in plants has been highly controversial. We have isolated and characterized for the first time in plants two cDNAs encoding rhodanese isoforms in Arabidopsis thaliana, AtRDH1 and AtRDH2. Both cDNAs contained a full-length open reading frame, the expression of which increased the rhodanese activity of transgenic yeast. AtRDH1 protein was mitochondrial, while AtRDH2 was cytosolic. AtRDH1 and AtRDH2 genes originated from the duplication of a large genomic region in chromosome 1 which took place before the appearance of the Arabidopsis genus. Our results confirm the existence of rhodanese in plants.     

Interspecies differences in rhodanese (thiosulfate sulfurtransferase, EC 2.8.1.1) activity in liver, kidney and plasma

Rhodanese levels have been measured in liver, kidney and plasma from a number of species. Liver activity was low in marmosets, pigeons and beagle bitches. Levels were high in rats and somewhat lower in hamsters and guinea pigs while levels in two strains of rabbits were intermediate between guinea pigs and marmosets. The relationship between hepatic and plasma rhodanese and cyanide sensitivity is discussed.     

Comparative studies on the distribution of rhodanese and beta-mercaptopyruvate sulfurtransferase in different organs of sheep (Ovis aries) and cattle (Bos taurus)

1. The activities of rhodanese and beta-mercaptopyruvate sulfurtransferase (MST) in different organs of sheep and cattle were measured. 2. Liver, kidney, omasum, and rumen were the richest sources of both enzymes. The activities of both enzymes in other organs of the sheep and the cattle decreased in the order of lung, brain, heart, abomasum, lymph node, urinary bladder, spleen, and the skeletal muscle. 3. The activities of both enzymes in most organs of the sheep were higher than the cattle. 4. Both enzymes showed higher activities in the epithelial layers than the muscular layers of rumen, omasum and reticulum. 5. In most of the tissues of both species the level of rhodanese activity was greater than MST.     

Circadian and ultradian (12 h) rhythms of hepatic thiosulfate sulfurtransferase (rhodanese) activity in mice during the first two months of life

Thiosulfate sulfurtransferase (TST) is an important 'enzyme of protection,' that accelerates the detoxification of cyanide, converting it into thiocyanate. The TST physiological rhythm was investigated at wks 2, 4, and 8 of post-natal development (PND) in the mouse. The results revealed a statistically significant gender-related difference, with the highest activity in females, at all the documented PND stages. In the second week of PND (pre-weaning time), the circadian rhythm of the enzyme activity was associated with ultradian components. The prominent circadian rhythm (τ=24 h) peaked at the beginning of the light span, more precisely ∼3 HALO (Hours After Light Onset). A week after weaning (wk 4 of PND), an impairment of the rhythm, with the peak shifted toward the second half of photophase, was recorded. Four to 6 wks later, about wk 8 of PND, the circadian rhythm pattern was stabilized, with its peak then located at the beginning of the dark span (13 HALO). The obtained results showed a 12 h phase-shift of the circadian TST peak time during PND, suggesting that the rhythm stabilization is age-dependent.     

Escherichia coli GlpE is a prototype sulfurtransferase for the single-domain rhodanese homology superfamily.

BACKGROUND: Rhodanese domains are structural modules occurring in the three major evolutionary phyla. They are found as single-domain proteins, as tandemly repeated modules in which the C-terminal domain only bears the properly structured active site, or as members of multidomain proteins. Although in vitro assays show sulfurtransferase or phosphatase activity associated with rhodanese or rhodanese-like domains, specific biological roles for most members of this homology superfamily have not been established. RESULTS: Eight ORFs coding for proteins consisting of (or containing) a rhodanese domain bearing the potentially catalytic Cys have been identified in the Escherichia coli K-12 genome. One of these codes for the 12-kDa protein GlpE, a member of the sn-glycerol 3-phosphate (glp) regulon. The crystal structure of GlpE, reported here at 1.06 A resolution, displays alpha/beta topology based on five beta strands and five alpha helices. The GlpE catalytic Cys residue is persulfurated and enclosed in a structurally conserved 5-residue loop in a region of positive electrostatic field. CONCLUSIONS: Relative to the two-domain rhodanese enzymes of known three-dimensional structure, GlpE displays substantial shortening of loops connecting alpha helices and beta sheets, resulting in radical conformational changes surrounding the active site. As a consequence, GlpE is structurally more similar to Cdc25 phosphatases than to bovine or Azotobacter vinelandii rhodaneses. Sequence searches through completed genomes indicate that GlpE can be considered to be the prototype structure for the ubiquitous single-domain rhodanese module.     

Multivariate factor analysis of sulfur oxidation and rhodanese activity in soils

The role of rhodanese as an intermediate catalyst in the oxidation of elemental S (S°) is not well understood. This study investigated the effect of 26 soil properties and steam sterilization in relation to S° oxidation and rhodanese activity in 33 soils (27 Oregon soils and six Chinese soils). S° oxidation potential was determined by incubating (7 d at 23 °C) soil amended with 500 mg S° kg^-1 soil and measuring the SO₄ released. Both total S° oxidation (TSO) and rhodanese activity varied widely among the 33 soils, ranging from 0 to 143 mg SO₄-S kg^-1 soil 7 d^-1 and 22 to 2109 nmoles SCN^- g^-1 soil h^-1 respectively. S° oxidation but not rhodanese activity had a significant positive correlation with soil pH. In sterile soils, chemical S° oxidation (CSO) averaged 3% of the total S° oxidation and apparent rhodanese activity averaged 11% of the total rhodanese activity. S° oxidation was not significantly correlated with rhodanese activity. However, development of stepwise regression models predicting S° oxidation revealed that rhodanese activity was an important explanatory variable in predicting biological S° oxidation (TSO minus CSO). Also, microbial biomass C was found to be an important parameter in models for both S° oxidation and rhodanese activity. Investigations of the effect of acidification during S° oxidation showed that biological S° oxidation was negatively correlated with S° oxidation-induced-pH-change for soils with pH > 6 but no such significant relationship was found on soils with pH> 6. This suggested that extreme acidity may inhibit S° oxidation but not rhodanese activity.     

Nitrification in coniferous forest soils

Net nitrification rates tend to be low or negligible in the forest floor of many coniferous forests of North-East Scotland. The most likely process controls are substrate availability, pH, allelopathy, water potential, nutrient status and temperature. These are discussed in relation to field and laboratory studies of net and potential rates of nitrification.Fungi make up by far the largest part of the nitrifier community in the coniferous forest floor. Very little is known about the distribution and activity of autotrophs in these systems, although it is certain that in vitro evidence suggesting autotrophs cannot nitrify at pH levels characteristic of coniferous forest soils is unrealistic.Because of the metabolic diversity of nitrifying fungi, a variety of organic and inorganic nitrification pathways may exist in coniferous forests. The possible involvement of free radicles in fungal nitrification in coniferous forest soils is also suggested.A complete understanding of nitrification in coniferous forest soils can only result from field characterisation of N flux such as through the use of ¹⁵N. This must be combined with ecophysiological characterisation of the organisms involved in order that the complexity of nitrification in coniferous forest soils can be resolved.     

Histochemical detection of thiosulphate sulphurtransferase (rhodanese) activity

Summary The distribution of superficial histological stains on tooth samples can be demonstrated in the scanning electron microscope (SEM) due to the absorption by the stain of the auto-cathodoluminescence (light) arising from the underlying substrate. Practical procedures by which this has been achieved are described.     

Effects of thiazolidine-4(R)-carboxylates and other low-molecular-weight sulfur compounds on the activity of mercaptopyruvate sulfurtransferase, rhodanese and cystathionase in Ehrlich ascites tumor cells and tumor-bearing mouse liver

Summary Changes of the specific activity of 3-mercaptopyruvate sulfurtransferase (MPST), rhodanese and cystathionase in Ehrlich ascites tumor cells (EATC) and tumor-bearing mouse liver after intraperitoneal administration of thiazolidine derivatives, L-cysteine, D,L-methionine, thiocystine or thiosulfate were estimated. Thiazolidine derivatives used were: thiazolidine-4-carboxylic acid (CF), 2-methyl-thiazolidine-2,4-dicarboxylic acid (CP) and 2-methyl-thiazolidine-4-carboxylic acid (CA). In the liver, the activity of MPST was significantly increased by all the studied compounds, whereas the activity of rhodanese was by CF and thiocystine and that of cystathionase was by the administration of cysteine and CP. Un the other hand, cysteine lowered the rhodanese activity and the activity of cystathionase was decreased by the administration of methionine and thiocystine. Activities of MPST and rhodanese were even lower in EATC than those in the liver of tumor-bearing mouse and the activity of cystathionase in EATC was not be detected. The thiazolidine derivatives significantly increased the level of MPST activity in EATC, but decreased the rhodanese activity. Thiosulfate also increased the activity of MPST to a lesser degree, but cysteine, methionine and thiocystine gave little change in the activity. The rhodanese activity in EATC was slightly increased only by thiocystine. These findings suggest that the sulfur metabolism in the tumor-bearing mouse liver is different from that in the normal mouse liver, and that sulfur compounds are minimally metabolized to sulfane sulfur, a labile sulfur, in EATC.     

Geochemical aspects of aluminium in forest soils in Galicia (N.W. Spain)

The aqueous speciation of Al was studied in acid forest soils in N.W. Spain. Aluminum concentrations were 10–70 mol L^–1, with variable proportions oflabile, nonlabile, andacid-soluble Al. Almost all thelabile Al was found complexed with F^–, Al³⁺ concentrations being low. The importance of organic matter was seen in the formation of Al-organic complexes in the solid soil fraction and the presence of aqueous alumino-organic complexes in superficial horizons (umbric epipedons) rich in organic matter.     

Heterotrophic nitrification in add forest soils

Ninety cultures of heterotrophic organisms were isolated from soils of four acid Norwegian forest sites, which were active in nitrifying. The isolates were tested for ability to form nitrite in a glucose-ammonium-inorganic salts medium. Eleven cultures were found capable of oxidizing ammonium to nitrite. The nitrifying organisms consist of 4 bacteria and 7 fungi.     

Water-soluble organic matter in forest soils

By applying a modified gel permeation technique, the molecular-size distribution (MSD) and complexing properties of water-soluble organic matter (WSOM), isolated from the A_h horizon under stands with either Douglas-fir, European beech or Scots pine were established. Both with respect to MSD and complexing properties, the dissolved organic matter was highly similar. WSOM was comprised of compounds apparently high in molecular weight (>1 kDa) and with a complexing capacity of 1.0±0.1 mol mg^–1 carbon as determined for Cu(II) at pH 5.5 and 0.01 M ionic strength. The effect of WSOM on the partitioning of cations between soil solid phase and soil solution was evaluated in several soil batch experiments using loamy sand or sandy soil material. Although a large part of WSOM was sorbed to the soil matrix, Al, Cu, Fe and Pb were solubilized in considerable amounts by complexation. The Mn concentration in the soil solution was also significantly increased but this probably resulted from a redox reaction, with certain constituents of WSOM serving as electron donor. With a decrease in soil pH, cation mobilization by WSOM was significantly lower as a result of increased sorption and a decrease in complexing capacity of the soluble organics. Application of several low MW aliphatic and phenolic acids gave results similar to the results obtained with WSOM.     

Rhodanese (thiosulfate:cyanide sulfurtransferase) from frog Rana temporaria

The molecular mass of rhodanese from the mitochondrial fraction of frog Rana temporaria liver, equaling 8.7 kDa, was determined by high-performance size exclusion chromatography (HP-SEC). The considerable difference in molecular weight and the lack of common antigenic determinants between frog liver rhodanese and bovine rhodanese suggest the occurrence of different forms of this sulfurtransferase in the liver of these animals.     

Conversion of 15N-ammonium in forest soils

To determine the fate of atmospheric ammonium in forest soils, one calcareous and two acid forest soils were incubated with ¹⁵N ammonium. In the calcareous soil about 65% of the applied ¹⁵N-ammonium was recovered as nitrate after 98 days of incubation, whereas in the acid soils less than 10% of the ¹⁵N-ammonium was converted to nitrate. In all soils a large proportion of the ¹⁵N was incorporated in organic nitrogen compounds. This incorporation limits the use of ¹⁵N tracers for the elucidation of the fate of atmospheric ammonium in soils.     

Thiosulfate sulfur transferases (Rhodaneses) ofChlorobium vibrioforme f.thiosulfatophilum

Two enzymes containing thiosulfate sulfur transferase activity were purified fromChlorobium vibrioforme f.thiosulfatophilum by ion exchange chromatography, gel filtration and isoelectrofocusing. Enzyme I is a basic protein with an isoelectric point at pH 9.2 and has a molecular weight of 39,000. TheK _m-values for thiosulfate and cyanide of the purified basic protein were 0.25 mM (thiosulfate) and 5 mM (cyanide). Enzyme II is an acidic protein. The enzyme has an isoelectric point at pH 4.6–4.7 and a molecular weight of 34,000. TheK _m-values of the acidic protein were found to be 5 mM for thiosulfate and 125 mM for cyanide.In addition to thiosulfate sulfur transferase activity, cellfree extracts ofChlorobium vibrioforme f.thiosulfatophilum also contained low thiosulfate oxidase activity and negligible thiosulfate reductase activity. The percent distribution of thiosulfate sulfur transferase and thiosulfate oxidase activities in the organism was independent of the offered sulfur compound (thiosulfate, sulfide or both) in the medium.Abbreviations C Chlorobium - SDS sodium dodecylsulfate Dedicated to Prof. Dr. Norbert Pfennig on the occasion of his 60th birthday     

Field determination of denitrification in water-logged forest soils

Abstract Denitrification rates were measured as N₂O production in two water-logged forest soils at monthly intervals. The effect of acetylene inhibition and the addition of nitrate, glucose, acetate and celloboise in field incubations was examined.
N₂O release from the two soils was very low, 26 mg N₂m⁻²y⁻¹ in ash and 178 mg N₂ in alder. In acetylene inhibited incubations N₂O production was higher, 296 and 486 mg N₂m⁻² y⁻¹ in ash and alder respectively. After addition of nitrate and C-sources to a 10 mM concentration, denitrification rates increased to 5–15 times higher values.
The denitrification rates below 4°C were low and most N₂O was produced in late spring and summer.
The highest rate of denitrification during a 50 h incubation experiment occurred between 3 and 23 h.