Subcellular Localization of the Starch Degradative and Biosynthetic Enzymes of Spinach Leaves 1
AUTOR(ES)
Okita, Thomas W.
RESUMO
The subcellular localization of the starch biosynthetic and degradative enzymes of spinach leaves was carried out by measuring the distribution of the enzymes in a crude chloroplast pellet and soluble protein fraction, and by the separation on sucrose density gradients of intact organelles, chloroplasts, peroxisomes, and mitochondria of a protoplast lysate. ADP-Glucose pyrophosphorylase, starch synthase, and starch-branching enzymes are quantitatively associated with the chloroplasts. The starch degradative enzymes amylase, R-enzyme (debranching activity), phosphorylase, and D-enzyme (transglycosylase) are observed both in the chloroplast and soluble protein fractions, the bulk of the degradative enzyme activities reside in the latter fraction. Chromatography of a chloroplast extract on diethylaminoethyl-cellulose resolves the R- and D-enzymes from amylase and phosphorylase activities although the two latter enzyme activities coeluted. The digestion pattern of amylase with amylopectin as a substrate indicates an endolytic activity but displays properties unlike the typical α-amylase as isolated from endosperm tissue.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=543051Documentos Relacionados
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