Publications

• O-Acetylserine sulfhydrylase and S-sulfocysteine synthase activities of Rhodospirillum tenue.

  Hensel G., Truper H.G.

  O-Acetylserine sulfhydrylase in cell-free extracts of Rhodospirillum tenue was markedly repressed after growth in the presence of sulfide or thiosulfate, whereas S-sulfocysteine synthase activity remained almost unchanged. Purification on DE52 cellulose resulted in the separation of two proteins: ... >> More

  O-Acetylserine sulfhydrylase in cell-free extracts of Rhodospirillum tenue was markedly repressed after growth in the presence of sulfide or thiosulfate, whereas S-sulfocysteine synthase activity remained almost unchanged. Purification on DE52 cellulose resulted in the separation of two proteins: Protein I with a molecular weight of 57000 had O-acetylserine sulfhydrylase activity only, while protein II with a molecular weight of 46000 had S-sulfocysteine synthase activity in addition. The activity of protein II with O-acetylserine plus sulfide was about 1.5 of that with O-acetylserine plus thiosulfate. Protein I from sulfate-grown cells possessed 74% of the total O-acetylserine sulfhydrylase, protein II 26%. Growth with sulfide repressed only the synthesis of protein I, which after separation showed only 19% of the measurable O-acetylserine sulfhydrylase, whereas protein II now possessed 81%. Regulatory and kinetic phenomena of the two activities were studied. In addition to the phototrophic bacteria studied earlier, also Rhodomicrobium vannielii, Rhodopseudomonas acidophila, Rhodocyclus purpureus and Thiocystis violacea were found to contain O-acetylserine sulfhydrylase activities; the latter two species contained S-sulfocysteine synthase activities in addition. << Less

  Arch Microbiol 134:227-232(1983) [PubMed] [EuropePMC]

• S-sulfocysteine synthase function in sensing chloroplast redox status.

  Gotor C., Romero L.C.

  The minor chloroplastic O-acetylserine(thiol)lyase isoform encoded by the CS26 gene in Arabidopsis thaliana has been described as an S-sulfocysteine synthase enzyme that plays an important role in chloroplast function. This enzyme is located in the thylakoid lumen, and its S-sulfocysteine activity ... >> More

  The minor chloroplastic O-acetylserine(thiol)lyase isoform encoded by the CS26 gene in Arabidopsis thaliana has been described as an S-sulfocysteine synthase enzyme that plays an important role in chloroplast function. This enzyme is located in the thylakoid lumen, and its S-sulfocysteine activity is essential for the proper photosynthetic performance of the chloroplast under long-day growth conditions. Based on the present knowledge of this enzyme, we suggest that S-sulfocysteine synthase functions as a protein sensor to detect the accumulation of thiosulfate as a result of the inadequate detoxification of reactive oxygen species generated under conditions of excess light to produce the S-sulfocysteine molecule that triggers protection mechanisms of the photosynthetic apparatus. << Less

  Plant Signal. Behav. 8:0-0(2013) [PubMed] [EuropePMC]

• Enzymatic proof for the identity of the S-sulfocysteine synthase and cysteine synthase B of Salmonella typhimurium.

  Nakamura T., Iwahashi H., Eguchi Y.

  S-Sulfocysteine synthase was isolated from Salmonella typhimurium LT-2 to homogeneous form with polyacrylamide gel electrophoresis. The molecular weight of this enzyme was determined to be ca. 55,000. The enzyme consisted of two identically sized subunits, and it contained one pyridoxal phosphate ... >> More

  S-Sulfocysteine synthase was isolated from Salmonella typhimurium LT-2 to homogeneous form with polyacrylamide gel electrophoresis. The molecular weight of this enzyme was determined to be ca. 55,000. The enzyme consisted of two identically sized subunits, and it contained one pyridoxal phosphate per subunit. The enzyme catalyzed the biosynthesis of cysteine or S-methylcysteine from sulfide or methanethiol and O-acetylserine, respectively, in addition to the formation of S-sulfocysteine from thiosulfate and O-acetylserine. The enzyme is identical to cysteine synthase B. The intracellular level of this enzyme was regulated by lesser extents of the same factors as those effective for cysteine synthase A. << Less

  J Bacteriol 158:1122-1127(1984) [PubMed] [EuropePMC]

• Arabidopsis S-sulfocysteine synthase activity is essential for chloroplast function and long-day light-dependent redox control.

  Bermudez M.A., Paez-Ochoa M.A., Gotor C., Romero L.C.

  In bacteria, the biosynthesis of Cys is accomplished by two enzymes that are encoded by the cysK and cysM genes. CysM is also able to use thiosulfate as a substrate to produce S-sulfocysteine. In plant cells, the biosynthesis of Cys occurs in the cytosol, mitochondria, and chloroplasts. Chloroplas ... >> More

  In bacteria, the biosynthesis of Cys is accomplished by two enzymes that are encoded by the cysK and cysM genes. CysM is also able to use thiosulfate as a substrate to produce S-sulfocysteine. In plant cells, the biosynthesis of Cys occurs in the cytosol, mitochondria, and chloroplasts. Chloroplasts contain two O-acetylserine(thiol)lyase homologs, which are encoded by the OAS-B and CS26 genes in Arabidopsis thaliana. An in vitro enzymatic analysis of the recombinant CS26 protein demonstrated that this isoform possesses S-sulfocysteine synthase activity and lacks O-acetylserine(thiol)lyase activity. In vivo functional analysis of this enzyme in knockout mutants demonstrated that mutation of CS26 suppressed the S-sulfocysteine synthase activity that was detected in the wild type; furthermore, the cs26 mutants exhibited a reduction in size and showed paleness, but penetrance of the growth phenotype depended on the light regime. The cs26 mutant plants also had reductions in chlorophyll content and photosynthetic activity (neither of which were observed in oas-b mutants) as well as elevated glutathione levels. However, cs26 leaves were not able to properly detoxify reactive oxygen species, which accumulated to high levels under long-day growth conditions. The transcriptional profile of the cs26 mutant revealed that the mutation had a pleiotropic effect on many cellular and metabolic processes. Our findings reveal that S-sulfocysteine and the activity of S-sulfocysteine synthase play important roles in chloroplast function and are essential for light-dependent redox regulation within the chloroplast. << Less

  Plant Cell 22:403-416(2010) [PubMed] [EuropePMC]

• Photosynthetic adaptation to length of day is dependent on S-sulfocysteine synthase activity in the thylakoid lumen.

  Bermudez M.A., Galmes J., Moreno I., Mullineaux P.M., Gotor C., Romero L.C.

  Arabidopsis (Arabidopsis thaliana) chloroplasts contain two O-acetyl-serine(thiol)lyase (OASTL) homologs, OAS-B, which is an authentic OASTL, and CS26, which has S-sulfocysteine synthase activity. In contrast with OAS-B, the loss of CS26 function resulted in dramatic phenotypic changes, which were ... >> More

  Arabidopsis (Arabidopsis thaliana) chloroplasts contain two O-acetyl-serine(thiol)lyase (OASTL) homologs, OAS-B, which is an authentic OASTL, and CS26, which has S-sulfocysteine synthase activity. In contrast with OAS-B, the loss of CS26 function resulted in dramatic phenotypic changes, which were dependent on the light treatment. We have performed a detailed characterization of the photosynthetic and chlorophyll fluorescence parameters in cs26 plants compared with those of wild-type plants under short-day growth conditions (SD) and long-day growth conditions (LD). Under LD, the photosynthetic characterization, which was based on substomatal CO(2) concentrations and CO(2) concentration in the chloroplast curves, revealed significant reductions in most of the photosynthetic parameters for cs26, which were unchanged under SD. These parameters included net CO(2) assimilation rate, mesophyll conductance, and mitochondrial respiration at darkness. The analysis also showed that cs26 under LD required more absorbed quanta per driven electron flux and fixed CO(2). The nonphotochemical quenching values suggested that in cs26 plants, the excess electrons that are not used in photochemical reactions may form reactive oxygen species. A photoinhibitory effect was confirmed by the background fluorescence signal values under LD and SD, which were higher in young leaves compared with mature ones under SD. To hypothesize the role of CS26 in relation to the photosynthetic machinery, we addressed its location inside of the chloroplast. The activity determination and localization analyses that were performed using immunoblotting indicated the presence of an active CS26 enzyme exclusively in the thylakoid lumen. This finding was reinforced by the observation of marked alterations in many lumenal proteins in the cs26 mutant compared with the wild type. << Less

  Plant Physiol. 160:274-288(2012) [PubMed] [EuropePMC]