Subunit potato tuber

Table 8 Activity of smaii and iarge subunit potato tuber ADP-Gic PPase mutants...

Enterotoxigenic E. coli B subunits of the heat labile toxin (LTB) Potato tuber Receptor-binding activity. Immunogenic in mice and humans when administered orally. Partially protective in mouse gut fluid assay. 24-26, 90... 

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... 

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... 

Figure 4.2 Crystal structure of potato tuber ADP-glucose small (catalytic) subunit monomer. The catalytic domain is in yellow and the beta-helix domain is in pink. ADPGlc is shown in atom type carbon atoms are green, oxygen atoms are red, nitrogen atoms are blue, phosphorus atoms are magenta, and the sulfate group is orange. (The full color version ofthis figure can be found atwww.Elsevier.books.com/)...

Residues that are not identical but similar in potato tuber ADP-glucose pyrophosphorylase large subunit. 

Earlier studies on the properties of phosphorylases isolated from various sources have indicated that their subunits are similar in size with about 100,000 daltons.15-17 The reaction proceeds in a rapid equilibrium random Bi-Bi mechanism as has been shown by kinetic studies with rabbit skeletal muscle phosphorylases a18-20 and b,21,22 rabbit liver enzyme,23 potato tuber enzyme,24 and the enzyme from E. coli.25) In contrast, the substrate specificities for various glucans differ considerably depending on the enzyme sources. The rabbit muscle enzyme has high affinity for branched glucans such as glycogen and amylopectin but low affinity for amylose and maltodextrin.26,27 The potato tuber enzyme can act on amylose, amylopectin, and maltodextrin but only poorly on glycogen,28,29 while the E. coli enzyme shows high affinity for maltodextrin.10 ... 

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... 

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