Potatoes ADPGlc PPase

In the case of potato tuber ADPGlc PPase, the large subunit greatly increases the affinity of the small (catalytic) subunit for 3 PGA and lowers its affinity for the inhibitor, pi.55 56 in a plant, there may be only one conserved small (catalytic) subunit and several large (regulatory) subunits that can be distributed in different parts of the plant.83,87 This is of physiological importance, as expression of different large subunits... 

Crystal Structure of Potato Tuber ADPGlc PPase... 

The crystal structure of the potato tuber homotetrameric small (catalytic) subunit ADPGlc PPase has been determined to 2.1 A resolution.64 The structures of the... 

The ADPGlc PPase from potato tuber behaves similarly to the enzyme from plant leaves. It has been purified to apparent homogeneity (56.9U/mg), and it was the first plant heteromeric enzyme to be expressed fully active in E. coli.52>53,55,56 Immunolocalization of the ADPGlc PPase in developing potato tuber cells has shown that the enzyme is localized in the amyloplast.127... 

A direct relationship between the increase in the activities of starch synthase and ADPGlc PPase, and the rate of starch accumulation, has been reported for developing maize endosperm (Ozbun et al., 1973), wheat grain (Moore and Turner, 1969 Turner, 1969), and potato tubers (Sowokinos, 1976) (for a review of these, see Preiss and Levi, 1980). 

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. 

The potato tuber ADPGlc PPase has been highly purified and, by two-dimensional polyacrylamide gel electrophoresis, two polypeptides could be distinguished by their slight differences in molecular mass, 50,000 and 51,000, and in net charge (Okita et al., 1990). The tuber small subunit is... 

SITE-DIRECTED MUTAGENESIS OF LYS RESIDUES AT THE BINDING SITE FOR THE ALLOSTERIC ACTIVATOR IN THE SUBUNITS OF THE POTATO TUBER ADPGlc PPASE. EFFECT ON THE SENSITIVITY OF THE HOLOENZYME TO THE ACTIVATOR, 3PGAa... 

If the ADPGlc PPases from different sources have similar three-dimensional structures, the structure of one should help predict the secondary structure of another. The sequence of enzymes from E. coli and Anabaena, and also from the two subunits of the potato tuber enzyme, were analyzed using the PHD program. One general structure that fits all of... 

---