TY - JOUR

T1 - Three O-acetyl-L-serine(thiol)lyase isoenzymes from Arabidopsis catalyse cysteine synthesis and cysteine desulfuration at different pH values

AU - Burandt, Petra

AU - Schmidt, Ahlert

AU - Papenbrock, Jutta

N1 - Funding information:. The expert technical assistance of Pamela von Trzebiatowski is gratefully acknowledged. We thank PD Dr. R. Hell for providing purified OAS-TL C protein used in initial experiments, Dr. H. Hesse for sending us pCS-A, pCS-B and pCS-C cDNA clones and Dr. J. Meens for sequencing work. For the lessons in isolating organelles from Arabidopsis we would like to thank Prof. Dr. H.-P. Braun and Wolf Wehrhan. The work was financially supported by grants from the Deutsche Forschungsgemeinschaft (PA 764/1-1/2, SCH 307/15-1).

PY - 2002/1/1

Y1 - 2002/1/1

N2 - So far, 7 different genes of the β-substituted alanine synthase family coding for proteins with O-acetyl-L-serine(thiol)lyase activity (OAS-TL) have been identified in Arabidopsis. The differences with respect to function and regulation of these isoforms are not well understood. In the present work, we aimed to differentiate between three OAS-TL proteins, A, B, and C, which are presumably localized in the cytoplasm, in plastids, and in mitochondria, respectively. The mature proteins were expressed in E. coli and the pH optima for the formation of cysteine were determined to pH 8.0, pH 8.0, and pH 7.0, respectively. The purified recombinant OAS-TL proteins also catalysed the formation of hydrogen sulfide (H2S) and β-cyanoalanine from cysteine in the presence of dithiothreitol or KCN, respectively. The three isoenzymes differed in their Km for cysteine in the presence of dithiothreitol, but the Km for cysteine in the presence of KCN were almost identical. On a molar basis, the formation of H2S or cysteine by the OAS-TL proteins varied in relation to pH. For the determination of both enzyme activities, cysteine synthesis and cysteine desulfuration, in different compartments of plant cells, chloroplasts and mitochondria were isolated from Arabidopsis plants and the OAS-TL and L-cysteine desulfhydrase activities were determined. In conclusion, a) the evolution of H2S from higher plants originates from different enzyme reactions, and b) the side reactions of the OAS-TL proteins seem to contribute massively to the total H2S release of higher plants at least at higher pH values.

AB - So far, 7 different genes of the β-substituted alanine synthase family coding for proteins with O-acetyl-L-serine(thiol)lyase activity (OAS-TL) have been identified in Arabidopsis. The differences with respect to function and regulation of these isoforms are not well understood. In the present work, we aimed to differentiate between three OAS-TL proteins, A, B, and C, which are presumably localized in the cytoplasm, in plastids, and in mitochondria, respectively. The mature proteins were expressed in E. coli and the pH optima for the formation of cysteine were determined to pH 8.0, pH 8.0, and pH 7.0, respectively. The purified recombinant OAS-TL proteins also catalysed the formation of hydrogen sulfide (H2S) and β-cyanoalanine from cysteine in the presence of dithiothreitol or KCN, respectively. The three isoenzymes differed in their Km for cysteine in the presence of dithiothreitol, but the Km for cysteine in the presence of KCN were almost identical. On a molar basis, the formation of H2S or cysteine by the OAS-TL proteins varied in relation to pH. For the determination of both enzyme activities, cysteine synthesis and cysteine desulfuration, in different compartments of plant cells, chloroplasts and mitochondria were isolated from Arabidopsis plants and the OAS-TL and L-cysteine desulfhydrase activities were determined. In conclusion, a) the evolution of H2S from higher plants originates from different enzyme reactions, and b) the side reactions of the OAS-TL proteins seem to contribute massively to the total H2S release of higher plants at least at higher pH values.

KW - Arabidopsis thaliana

KW - Cysteine

KW - Desulfhydrase

KW - Sulfide

KW - β-cyanoalanine

UR - http://www.scopus.com/inward/record.url?scp=0036194827&partnerID=8YFLogxK

U2 - 10.1078/0176-1617-00611

DO - 10.1078/0176-1617-00611

M3 - Article

AN - SCOPUS:0036194827

VL - 159

SP - 111

EP - 119

JO - Journal of plant physiology

JF - Journal of plant physiology

SN - 0176-1617

IS - 2

ER -