PLANT PHYSIOLOGY , Vol 105, Issue 4 1393-1398, Copyright © 1994 by American Society of Plant Biologists
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METABOLISM AND ENZYMOLOGY |
Two Distinct Aldolases of Class II Type in the Cyanoplasts and in the Cytosol of the Alga Cyanophora paradoxa
W. Gross, M. G. Bayer, C. Schnarrenberger, U. B. Gebhart, T. L. Maier and HEA. Schenk
Institut fur Pflanzenphysiologie und Mikrobiologie, Freie Universitat Berlin, D-14195 Berlin, Germany (W.G., C.S)
Two aldolases from the alga Cyanophora paradoxa (Glaucocystophyta) can be
separated by chromatography on diethylaminoethyl-Fractogel. The two
aldolases are inhibited by 1 mM ethylene-diaminetetraacetate (EDTA) and,
therefore, are class II aldolases. When cells of C. paradoxa were
fractionated, one aldolase was associated with the cytosol fraction and the
other was associated with the cyanoplast fraction. The
Km(fructose-1,6-bisphosphate) was 600 [mu]M for the cytosolic aldolase and
340 [mu]M for the cyanoplast aldolase. The activity of the cytosolic
aldolase was increased up to 4-fold by 100 mM K+ and slightly inhibited by
Li+ and Cs+, whereas the cyanoplast aldolase was not affected by these
ions. Inactivation by 1 mM EDTA could be partly restored by the addition of
Co2+ or Mn2+ and to a lesser extent by Zn2+ or Mg2+. The molecular masses
of the native cytosolic and cyanoplast aldolases are about 90 and 85 kD,
respectively, as estimated by velocity centrifugation in sucrose gradients.
Implications for the evolution of class I and II aldolases in chloroplasts
of higher plants and algae will be discussed.
