Subunit potato leaf

The potato tuber, spinach leaf, and maize endosperm enzymes have small subunit masses of 50,000,51,000, and 54,000, respectively, and large subunit masses of 51,000, 54,000, and 60,000, respectively. The small and large subunits have about 50 to 60% identity with each other and have about 30 to 40% identity with the procaryotic ADPGlc PPases. 

ADP-Glc PPase from potato tuber has an intermolecular disulfide bridge that links the two small subunits by the Cys residue it can be activated by reduction of the Cys disul-hde linkage (46). At low concentrations (lOjxM) of 3-PGA, both spinach leaf reduced thioredoxin/ and m reduce and activate the enzyme. Fifty percent activation was observed for 4.5-and 8.7- xM reduced thioredoxin/ and m (47). The activation was reversed by oxidized thioredoxin. Cys is conserved in the ADP-Glc PPases from plant leaves and other tissues except for the monocot endosperm enzymes. In photosynthetic tissues, this reduction may also be physiologically pertinent in the hne regulation of the ADP-Glc PPase. 

Cholera toxin B subunit 0.3% TSP leaf, tuber (potato) 55... 

Other plant ADP-Glc PPases have been studied in detail and they also have been shown to be composed of two dissimilar subunits. ADP-Glc PPase from potato tuber is composed of two different subunits, 50 and 51 kDa, with oljPj heterotetrameric subunit structure. The small subunit of many higher plant ADP-Glc PPases is highly conserved among plants with 85-95% identity. The maize endosperm ADP-Glc PPase, of molecular mass of 230 kDa, reacts with the antibody prepared against the native spinach leaf enzyme in immunoblot experiments. The enzyme is composed of subunits of 55 and 60 kDa, which would correspond, respectively, to the spinach leaf 51 and 54kDa. " ... 

The sequences are listed in one letter code and were taken from Ballicora et a/. and Smith-White and Preiss." The Lys residues in bold are those covalehtly modified by pyridoxal-P in theAnabaena and spinach leaf enzymes and are highly conserved in other ADP-GIc PPases. In the case of the potato tuber enzyme the Lys residue was identified via site-directed mutagenesis experiments. The numbers 382 and 419 correspond to the Lys residues in the Anabaena ADP-GIc PPase subunit. The activator sites 1 and 2 are present in the small and large subunits of the plant ADP-GIc PPase. 

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