caa a22 4500 397521057 CHVBK 20180308164632.0 cr unu---uuuuu 161202e199505 xx s 000 0 eng 10.1093/jxb/46.5.531 doi (NATIONALLICENCE)oxford-10.1093/jxb/46.5.531 Stephan U.W. Institute of Plant Genetics and Crop Plant Research, Corrensstrasse 3, D-06466 Gatersleben, Germany The plant-endogenous Fe(II)-chelator nicotianamine restricts the ferrochelatase activity of tomato chloroplasts [Elektronische Daten] [U.W. Stephan] Stripped chloroplasts were prepared from young leaves of a tomato wild type (Lycopersicon esculentum Mill.) and its mutant chloronerva. Several morphological and biochemical abnormalities of this mutant are caused by the total lack of the plant-endogenous Fe2+ chelator nicotianamine (NA). The ferrochelatase activity was estimated by determination of 59Fe incorporated into haem. A mercaptoethanol concentration of 250 mM was necessary to maintain full enzyme activity. The reducing agent supported the reduced state of the active site of the enzyme more than that of the iron as revealed by use of ferrous and ferric ionproviding compounds as substrates. Chloroplasts of both genotypes exhibited a similar enzyme activity. NA inhibited this activity by nearly 100% depending on the concentration applied. On the basis of the formation constant of the Fe(ll)-NA complex and the concentrations of iron and NA in the enzyme assay as well as in the tomato shoot apex region it is proposed that ferrochelatase acts in vivo with an iron level at the attomolar range which is provided by NA. © Oxford University Press Research Papers nationallicence Ferrochelatase activity nationallicence ferrous ion concentration nationallicence nicotianamine nationallicence tomato chloroplasts nationallicence substrate limitation nationallicence Journal of Experimental Botany Oxford University Press 46/5(1995-05), 531-537 0022-0957 46:5<531 1995 46 exbotj https://doi.org/10.1093/jxb/46.5.531 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1093/jxb/46.5.531 text/html Onlinezugriff via DOI NATIONALLICENCE 100 1- Stephan U.W. Institute of Plant Genetics and Crop Plant Research, Corrensstrasse 3, D-06466 Gatersleben, Germany NATIONALLICENCE 773 0- Journal of Experimental Botany Oxford University Press 46/5(1995-05), 531-537 0022-0957 46:5<531 1995 46 exbotj Metadata rights reserved CC BY-NC-4.0 http://creativecommons.org/licenses/by-nc/4.0 nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-oxford