caa a22 4500 477110738 CHVBK 20180405111608.0 cr unu---uuuuu 170330e19960901xx s 000 0 eng 10.1007/BF00035055 doi (NATIONALLICENCE)springer-10.1007/BF00035055 Comparison of rhizobitoxine-induced inhibition of β-cystathionase from different bradyrhizobia and soybean genotypes [Elektronische Daten] [K. Xiong, J. Fuhrmann] The enzyme β-cystathionase catalyzes the conversion of cystathionine to homocysteine in both plants and bacteria. Preparations of this enzyme taken from both Salmonella and spinach (Spinacia oleracea L.) have been shown to be irreversibly inhibited by low concentrations of rhizobitoxine (RT), a chlorosis-inducing phytotoxin produced by some strains of soybean bradyrhizobia. The sensitivities of β-cystathionase from bradyrhizobia and soybean are not well characterized. Therefore, we purified β-cystathionase from selected bradyrhizobia and soybean genotypes that have been shown to exhibit differences in RT production and apparent RT sensitivities, respectively. Enzyme purified from E. coli strain DH52 was used for comparison. The enzymes differed in their physiological properties and RT sensitivities. Overall, the β-cystathionase enzymes purified from bradyrhizobia were more sensitive to RT than were those from the soybean cultivars. Kinetic studies showed that the nature of the RT-induced inhibition also differed between the two sources. The enzymes from bradyrhizobia exhibited inhibition that was [RT]-dependent, whereas the enzymes from soybean showed a time-dependent inhibition. These contrasting characteristics may in part reflect differences in active site accessibility, amino acid components, and associated RT diffusion rates. However, in all cases the inhibition caused by RT showed a typical substrate-competitive inhibition pattern. Kluwer Academic Publishers, 1996 β-cystathionase nationallicence rhizobitoxine nationallicence secondary RT inhibition constant nationallicence RT : rhizobitoxine nationallicence PLP : pyridoxal phosphate nationallicence DTT : dithioerythritol nationallicence PMSF : phenylmethylsulfonyl fluoride nationallicence HTP : hydroxyapatite nationallicence Xiong K. Delaware Agricultural Experiment Station, Department of Plant and Soil Sciences, College of Agricultural Sciences, University of Delaware, 19717-1303, Newark, DE, USA aut Fuhrmann J. Delaware Agricultural Experiment Station, Department of Plant and Soil Sciences, College of Agricultural Sciences, University of Delaware, 19717-1303, Newark, DE, USA aut Plant and Soil Kluwer Academic Publishers; http://www.wkap.nl 186/1(1996-09-01), 53-61 0032-079X 186:1<53 1996 186 11104 https://doi.org/10.1007/BF00035055 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/BF00035055 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Xiong K. Delaware Agricultural Experiment Station, Department of Plant and Soil Sciences, College of Agricultural Sciences, University of Delaware, 19717-1303, Newark, DE, USA aut NATIONALLICENCE 700 1- Fuhrmann J. Delaware Agricultural Experiment Station, Department of Plant and Soil Sciences, College of Agricultural Sciences, University of Delaware, 19717-1303, Newark, DE, USA aut NATIONALLICENCE 773 0- Plant and Soil Kluwer Academic Publishers; http://www.wkap.nl/ 186/1(1996-09-01), 53-61 0032-079X 186:1<53 1996 186 11104 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer