Catalytic implications of the higher plant ADP-glucose pyrophosphorylase large subunit

Our mutagenesis and kinetic analyses of the large subunit of the potato AGPase heterotetramer suggest that the large subunit is essential not only for allosteric regulation but also for catalysis of the enzyme. The catalytic significance of the large subunit is further emphasized by photoaffinity labeling experiment with ATP analog which shows that the large subunit binds ATP as efficiently as the small subunit.