Open AccessCO 2 is the inorganic carbon substrate of NADP malic enzymes from Zea mays and from wheat germ
Author(s) -
HäSLER Rainer E.,
HOLTUM Joseph A. M.,
LATZKO Erwin
Publication year - 1987
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1111/j.1432-1033.1987.tb10911.x
Subject(s) - enzyme , wheat germ , zea mays , malic enzyme , substrate (aquarium) , c4 photosynthesis , chemistry , germ , biochemistry , malic acid , botany , biology , dehydrogenase , agronomy , ecology , citric acid , microbiology and biotechnology
NADP malic enzyme (EC 1.1.1.40) was extracted and partially purified from the green leaves of Zea mays var . Felix and from wheat germ. The active inorganic carbon species for both enzymes was, in contrast to an earlier report, CO 2 not HCO − 3 . The apparent K m , co 2 , for the maize enzyme was 1.2 mM and the apparent K m , co 2 , for the wheat germ preparation was 4.2 mM under conditions of substrate saturation, pH 7.3 and 17°C. These observations support the views that CO 2 , rather than HCO 3 − as has been suggested, is produced in bundlesheath chloroplasts and that the reaction mechanism catalysed by plant cytosolic and chloroplastic NADP malic enzymes is similar to that proposed for avian NADP malic enzymes.