Kinases fructose phosphat kinase

Fructose- -phosphate kinase from rabbit muscle 84,000... 

As discussed in Section 22.7, illumination of chloroplasts leads to light-driven pumping of protons into the thylakoid lumen, which causes pH changes in both the stroma and the thylakoid lumen (Figure 22.27). The stromal pH rises, typically to pH 8. Because rubisco and rubisco activase are more active at pH 8, COg fixation is activated as stromal pH rises. Fructose-1,6-bisphosphatase, ribulose-5-phosphate kinase, and glyceraldehyde-3-phosphate dehydrogenase all have alkaline pH optima. Thus, their activities increase as a result of the light-induced pH increase in the stroma. 

Sabri Ml, Ederle K, Holdsworth CE, et al. 1979b. Studies on the biochemical basis of distal axonipathies. II. Specific inhibition of fructose-6-phosphate kinase by 2,5-hexanedione and methyl-butyl ketone. Neurotoxicologly 1 285-297. 

Fructose 6-phosphate kinase (phosphofructo-kinase) has attracted much attention because of its regulatory properties (Chapter n).880-882 Prokaryotic forms are somewhat simpler.883 The related fructose 6-phosphate 2-kinase is a component of a bifunctional kinase-phosphatase (Fig. 11-2, steps d and e) and has a structure similar to that of adenylate kinase.884... 

Fructose bisphosphate aldolases 699 Fructose 6-phosphate 535, 693s Fructose 6-phosphate kinase 656 Fructose-1,6-bisphosphatase 645 Fructose-2,6-bisphosphatase 646 Fruit fly. See Drosophilia melanogaster Fucose (Fuc) 165s L-Fucose isomerase 693 Fucosyltransferase 184 Fucoxanthin 22... 

Answer Ribulose 5-phosphate kinase, fructose 1,6-bisphosphatase, sedoheptulose 1,7-bisphosphatase, and glyceraldehyde 3-phosphate dehydrogenase would be inhibited. All have mechanisms requiring activation by reduction of a critical disulfide bond to a pair of —SH groups. Iodoacetate reacts irreversibly with free —SH groups. 

The enzyme that catalyzes the conversion of PEP to pyruvate is pyruvate kinase. Liver pyruvate kinase is stimulated allosterically by fructose-1,6-diphosphate, AMP, ADP, and glyceraldehyde-3-phosphate. It is inhibited by alanine, ATP, NADH, and, more importantly, by cAMP- and Ca2 calmodulin-controlled phosphorylation. High blood glucagon levels thus inhibit the activities of both PFK II and pyruvate kinase in the liver through phosphorylation. Transcription of pyruvate kinase is also decreased by glucagon and increased by insulin. Muscle pyruvate kinase is not subject to cAMP or Ca2+ regulation. The pyruvate kinase reaction is practically irreversible. 

A similar conclusion was arrived at by Arnold and Pette ( 2) from studies carried out on the in vitro binding of aldolase glyceraldehyde phosphate dehyrogenase, fructose-6-phosphate kinase, phosphoglycerate kinase, pyruvate kinase and lactate dehydrogenase to the structural proteins F-actin, myosin, acto-myosin and stromaprotein. 

A. triose phosphate isomerase B. fructose-1-phosphate kinase... 

The crystal structure of the entire 6-phosphofructo-2-kinase/fructose 2,6-bisphosphatase, a key bifunctional regulator of both glycolysis and gluconeogenesis, has been solved at 2.0 A resolution. The entire enzyme is a homodimer of 55kDa subunits arranged in a head-to-head fashion, with each monomer consisting of an independent kinase and phosphatase domain. The location of y-5 -ATP and inorganic phosphate in the kinase and phosphatase domains,... 

Kitamura, K., Kangawa, K., Matsuo, H., Uyeda, K. (1988). Phosphorylation of myocardial fructose-6-phosphate,2-kinase fructose-2,6-bisphosphatase by cAMP-dependent protein kinase and protein kinase C. J. Biol. Chem. 263, 16796-16801. 

D-Fructose 1-phosphate kinase catalyzes the phosphorylation of D-fructose 1-phosphate to D-fructose 1,6-bisphosphate. The enzyme has been purified from Aerobacter aerogenes326 and Bacteroides symbiosis.327... 

The molecular weight is328 75,000, and the Km for D-fructose 1-phosphate is326 0.3 mM at an optimal327 pH of 8. No phosphorylation is observed with L-ffuctose 1-phosphate, D-mannose 6-phosphate, D-fructose 6-phosphate, D-glucose 6-phosphate, or D-glucose 1-phosphate.328 The enzyme requires Mnz+ or Mg2+ for catalytic activity,328 but K+, Rb+, and NH4+ increase the enzymic activity.329 ATP inhibits the kinase, as the ratio of concentration of Mg2+ to ATP decreases below 2 1. The ATP inhibition can be released by Mg2+. Citrate (K, 0.85 mM), D-fructose 1,6-bisphosphate (K,- 4.4 mM), and D-fructose 6-phosphate (Kj 1.0 mM) inhibit D-fructose 1-phosphate kinase competitively with D-fructose 1-phosphate.328... 

Termonia and Ross (1981-1,2) developed a reaction scheme coupling phosphofructo-kinase and pyruvate kinase reactions by referring to experimental observations of known activations and inhibitions of enzymes by metabolites. By numerical analysis of the rate equations they confirmed the oscillations in the concentrations of fructose-6-phosphate, pyruvate, phosphoenolpyruvate, fructose 1,6-biphosphate, and ADP. 

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