Phosphofructokinase reactions involving

The second indirect route involves the formation of fructose 6-phosphate from fructose 1,6-bisphosphate without the intervention of phosphofructokinase reaction. This route is catalyzed by fructose bisphosphatase ... 

The principle enzymes of glycolysis involved in regulation are hexokinase (reaction 1), phosphofructokinase (reaction 3), and pyruvate kinase (reaction 10) ... 

Mechanism for Gluconeogenesis. Since the glycolysis involves three energetically irreversible steps at the pyruvate kinase, phosphofructokinase, and hexokinase levels, the production of glucose from simple noncarbohydrate materials, for example, pyruvate or lactate, by a reversal of glycolysis ( from bottom upwards ) is impossible. Therefore, indirect reaction routes are to be sought for. 

Initial phosphorylations The formation of fructose bisphosphate occurs via two phosphorylation reactions that involve ATP hydrolysis, which are catalysed by hexokinase and phosphofructokinase ... 

Allosteric changes usually involve rate-determining reactions. For example, glycolysis in the liver is stimulated following a meal by an increase in fructose 2,6-bisphosphate, an allosteric activator of phosphofructokinase (see p. 98). Gluconeogenesis is inhibited by fructose 2,6-bisphosphate, an inhibitor of fructose 1,6-bisphos-phatase (see p. 118). 

Other forms of vanadium have been implicated in the stimulation of the plasma membrane vanadate-dependent NAD(P)H oxidation reaction. Decavanadate has been shown to be a more potent stimulator of the vanadate-dependent NADH oxidation activity than added orthovanadate [30,31], Interestingly, decavanadate reductase activity has been found to be an alternative activity of an NADP-specific isocitrate dehydrogenase [32], Diperoxovanadium derivatives have also been shown to be involved in this type of reaction [33,34], Decavanadate may play a role in the biological role of vanadium, as it is found in yeast cells growing in the presence of orthovanadate [8] and is a potent inhibitor of phosphofructokinase-1, the control step of glycolysis, and other metabolic reactions [35],... 

Citrate provides the precursors (acetyl-CoA, NADPH) for fatty acid synthesis and is a positive allosteric modulator of acetyl-CoA carboxylase, which is involved in the initiation of long-chain fatty acid synthesis (Chapter 18). It regulates glycolysis by negative modulation of 6-phosphofructokinase activity (see above). All of the above reactions occur in the cytoplasm, and citrate exits from mitochondria via the tricarboxylate carrier. 

The names of the enzymes involved in the ten successive glycolysis reaction steps, as per Figure 3.1, are (1) hexokinase, (2) hexose phosphateisomerase, (3) phosphofructokinase, (4) aldolase, (5) triosphosphate isomerase, (6) glyceraldehyde-... 

Four molecules of ATP are formed from ADP during glycolysis via substrate-level phosphorylation, which is catalyzed by enzymes in the cytosol (reactions 7 and 10). Unlike ATP formation in mitochondria and chloroplasts, a proton-motive force is not involved in substrate-level phosphorylation. Early In the glycolytic pathway, two ATP molecules are consumed one by the addition of a phosphate residue to glucose In the reaction catalyzed by hex okinase (reaction 1), and another by the addition of a second phosphate to fructose 6-phosphate In the reaction catalyzed by phosphofructokinase 1 (reaction 3). Thus glycolysis yields a net of only two ATP molecules per glucose molecule. 

The glycolytic pathway down to pyruvate involves 10 enzyme-catalyzed steps with three kinases that use ATP (Fig. 11-32). The reaction catalyzed by phosphofructokinase (PFK) plays the major part in controlling the overall flux of the whole pathway. It catalyzes the phosphorylation of fructose 6-phosphate (Fru6P) to fructose 1,6-bisphosphate (Frul6P2). Hexokinase and pyruvate kinase (PK) have relatively higher maximal velocities. PFK is the target for more effector molecules than the other two kinases (see Fig. 11-14). 

As discussed in section 5.7, the reverse of the glycolytic pathway is important as a means of glucose synthesis — the process of gluconeogenesis. Most of the reactions of glycolysis are readily reversible, but at three points (the reactions catalysed by hexokinase, phosphofructokinase and pyruvate kinase) there are separate enzymes involved in glycolysis and gluconeogenesis. 

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