PLANT PHYSIOLOGY , Vol 115, Issue 2 677-682, Copyright © 1997 by American Society of Plant Biologists
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BIOCHEMISTRY AND ENZYMOLOGY |
Partial Purification and Characterization of Red Chlorophyll Catabolite Reductase, a Stroma Protein Involved in Chlorophyll Breakdown
S. Rodoni, F. Vicentini, M. Schellenberg, P. Matile and S. Hortensteiner
Department of Plant Biology, University of Zurich, CH-8008 Zurich, Switzerland
Red chlorophyll (Chl) catabolite (RCC) reductase, which catalyzes the
reaction of an intermediary Chl catabolite (RCC) in the two-step cleavage
reaction of pheophorbide (Pheide) a into primary fluorescent catabolites
(pFCCs) during Chl breakdown, was characterized and partially purified. RCC
reductase activity was present at all stages of barley leaf development and
even in roots. The highest specific activity was found in senescent leaves,
which were used to purify RCC reductase 1000-fold. Among the remaining
three proteins, RCC reductase activity was most likely associated with a
55-kD protein. RCC reductase exhibited saturation kinetics for RCC, with an
apparent Michaelis constant of 0.6 mM. The reaction depended on reduced
ferredoxin and was sensitive to oxygen. Assays of purified RCC reductase
with chemically synthesized RCC as a substrate yielded three different
FCCs, two of which could be identified as the stereoisomeric pFCCs from
canola (Brassica napus) (pFCC-1) and sweet pepper (Capsicum annuum)
(pFCC-2), respectively. In the coupled reaction with Pheide a oxidase and
RCC reductase, either pFCC-1 or pFCC-2 was produced, depending on the plant
species employed as a source of RCC reductase. Data from 18 species suggest
that the stereospecific action of RCC reductase is uniform within a plant
family.