Fructose-1-6-diphosphate

This cleavage is a retro aldol reaction It is the reverse of the process by which d fruc tose 1 6 diphosphate would be formed by aldol addition of the enolate of dihydroxy acetone phosphate to d glyceraldehyde 3 phosphate The enzyme aldolase catalyzes both the aldol addition of the two components and m glycolysis the retro aldol cleavage of D fructose 1 6 diphosphate... 

Fructose-1,6-diphosphate (trisodium sait) [38099-82-0] M 406.1, pKj 6.14, pK 6.93 (free acid). For purification via the acid strychnine salt, see Neuberg, Lustig and Rothenberg [Arch Biochem 3 33 1943]. The calcium salt can be partially purified by soln in ice-cold M HCl (Ig per lOmL) and repptn by dropwise addition of 2M NaOH the ppte and supernatant are heated on a boiling water bath for a short time, then filtered and the ppte is washed with hot water. The magnesium salt can be pptd from cold aqueous soln by adding four volumes of EtOH. 

In order to give useful information about an enzyme, a conformationally restricted active-site-directed analog inhibitor need not bind to the enzyme irreversibly. In a study of the enzyme fructose 1,6-diphosphatase from rabbit liver, Benkovic et al, have investigated the question of the reactive form of the fructose 1,6-diphosphate in the enzymatic process (104,105). Three likely forms are shown in structures 50, 51 and 52. 

Each of these compounds, 53-56, was shown to be a very effective competitive inhibitor of the enzyme with respect to the fructose 1,6-diphosphate, whereas several other analogs, including acyclic structures, had no effect. These and other results suggest that the furanose form of the sugar diphosphate is the active form in the enzymatic reaction (105). More recent studies using rapid quenching techniques and C-nmr measurements have confirmed this hypothesis and indicate that the enzyme uses the a anomer 52 much more rapidly than the 3 anomer 50 and probably uses the a anomer exclusively (106). 

Kelley, P.M. Freeling, M. (1984b). Anaerobic expression of maize fructose-1,6-diphosphate aldolase. Journal of Biological Chemistry, 259,14180-3. 

Phosphofructokinase (PFK) is a key regulatory enzyme of glycolysis that catalyzes the conversion of fructose-6-phosphate to fructose-1,6-diphosphate. The active PFK enzyme is a homo- or heterotetrameric enzyme with a molecular weight of 340,000. Three types of subunits, muscle type (M), liver type (L), and fibroblast (F) or platelet (P) type, exist in human tissues. Human muscle and liver PFKs consist of homotetramers (M4 and L4), whereas red blood cell PFK consists of five tetramers (M4, M3L, M2L2, ML3, and L4). Each isoform is unique with respect to affinity for the substrate fructose-6-phosphate and ATP and modulation by effectors such as citrate, ATP, cAMP, and fructose-2,6-diphosphate. M-type PFK has greater affinity for fructose-6-phosphate than the other isozymes. AMP and fructose-2,6-diphosphate facilitate fructose-6-phosphate binding mainly of L-type PFK, whereas P-type PFK has intermediate properties. 

The hexose phosphate, fructose-1,6-diphosphate, is split by aldolase into two triose phosphates glyceraldehyde-3-phosphate and dihydroxyacetone phosphate. Aldolase consists of four 40-kDa subunits. Three tissue-specific forms exist in human tissues aldolase A (ubiquitous and very active in the muscle), aldolase B (liver, kidney, and small intestine), and aldolase C (specific to the brain). These three isozymes have nearly the same molecular size but differ in substrate specificity,... 

Pyruvate kinase (PK) is one of the three postulated rate-controlling enzymes of glycolysis. The high-energy phosphate of phosphoenolpyruvate is transferred to ADP by this enzyme, which requires for its activity both monovalent and divalent cations. Enolpyruvate formed in this reaction is converted spontaneously to the keto form of pyruvate with the synthesis of one ATP molecule. PK has four isozymes in mammals M, M2, L, and R. The M2 type, which is considered to be the prototype, is the only form detected in early fetal tissues and is expressed in many adult tissues. This form is progressively replaced by the M( type in the skeletal muscle, heart, and brain by the L type in the liver and by the R type in red blood cells during development or differentiation (M26). The M, and M2 isozymes display Michaelis-Menten kinetics with respect to phosphoenolpyruvate. The Mj isozyme is not affected by fructose-1,6-diphosphate (F-1,6-DP) and the M2 is al-losterically activated by this compound. Type L and R exhibit cooperatively in... 

The diagnosis of PK deficiency depends on the determination of quantitative enzyme activity or qualitative abnormalities of the enzyme. In 1979, the International Committee for Standardization in Haematology (ICSH) established methods for the biochemical characterization of red blood cell PK variants (M22). Since the establishment of these methods, many PK-deficient cases have been characterized, including 13 cases of homozygous PK deficiency. Residual red blood cell PK activity is not usually associated with phenotypic severity,whereas enzymatic characteristics such as decreased substrate affinity, thermal instability, or impaired response to the allosteric activator fructose-1,6-diphosphate (F-1,6-DP) correspond to a more severe phenotype. 

Brockamp, H.P, Kula, M.R. and Goetz, F. (1991) A robust microbial fructose-1,6-diphosphate aldolase its manufacture and use in sugar synthesis. DE3940431. 

Nicotinamide adenine dinucleotide (NAD) Fructose 1,6-diphosphate Glucose-6-phosphate Isopentenyl pyrophosphate Ribose-6-phosphate-l-pyrophosphate... 

A syringolide 45, an elicitor of the bacterial plant pathogen Pseudomonas Siringae pv. tomato, has been synthesized in five steps via a fructose 1,6-diphosphate aldolase reaction (Scheme 95) <2000JOC4529>. 

The essentially nonreversible formation of D-fructose 1-phosphate in the muscle-aldolase system is probably attributable to thermodynamic stabilization. D-Fructose 1-phosphate can form a stable pyranose structure, whereas D-fructose 1,6-diphosphate can exist only in the less stable furanose or acyclic forms.72(,) Only when the cleavage products are removed is the monophosphate effectively split under the influence of aldolase. 

I, 7-diphosphate.170 1 (f> This tetrose phosphate is involved with phosphoenol pyruvate in the formation of shikimic acid via 3-deoxy-2-keto-D-ara6ino-heptonic acid 7-phosphate and, hence, of aromatic compounds.170(d) A synthesis of the tetrose phosphate has been described.170 1 Aldolase shows a high affinity for the heptulose diphosphate and, compared with that for D-fructose 1,6-diphosphate, the rate of reaction is about 60 %. The enzyme transaldolase, purified 400-fold from yeast, catalyzes the following reversible reaction by transfer of the dihydroxyacetonyl group.l70(o>... 

With zymohexase, fructose 1,6-diphosphate, and acetaldehyde, a 5-de-oxypentulose 1-phosphate resulted,66 and, with a pea-aldolase preparation, the product was identified as 5-deoxy-D-ilireo-pentulose (LXI). Using... 

Fructose 1,6-diphosphatase hydrolyzes D-fructose 1,6-diphosphate to give D-fructose 6-phosphate and PO . It is a key enzyme in the gluconeo-genesis pathway. Two divalent metal ions (Mg2+, Mn2+, Zn2+, and Co2+) are involved in catalysis. In the enzyme isolated from pork kidney the metal-metal distance accounts to 3.7 A [12]. A reaction mechanism similar to that of protein phosphatase 1 was proposed, but leaving group stabilization by metal coordination of the ester oxygen atom appears to be absent (Figure 6) [12]. 

Radhaiah, V., K.V. Joseph, and K.J. Rao. 1989. Toxic effect of fenvalerate on fructose-1,6-diphosphate aldolase activity of liver, gill, kidney, and brain of the fresh water teleost, Tilapia mossambica. Bull. Environ. Contam. Toxicol. 42 150-153. 

Phosphofructokinase is an enzyme that catalyzes one of the steps in the degradation of carbohydrates. Initial rates of the reaction that converts fructose-6-phosphate (S) to fructose-1,6-diphosphate (P) as a function of c 0 (the initial fructose-6-diphosphate concentration) are as follows (the concentration of enzyme added, ce0, is the same in each case) ... 

Rao SB, Mehendale HM. 1989. Protection from chlordecone (Kepone)-potentiated carbon tetrachloride hepatotoxicity in rats by fructose 1,6-diphosphate. Int J Biochem 21(9) 949-954. 

Aldolase 4.1.2.3 C Fructose-1,6-diphosphate NADH Glyceraldehyde-3- phosphate Glycerophosphate dehydrogenase... 

Aldolase 4.1.2.3 Fructose-1,6-diphosphate Dihydroxyacetone phosphate Formation of a hydrazone... 

Von derOsten, C.H., Sinskey, A.J., Barbas El, C.F., Pederson, R.L., Wang, Y.F. and Wong, C.H., Use of a recombinant bacterial fructose-1,6-diphosphate aldolase in aldol reactions preparative syntheses of 1-deoxynojirimycin, 1-deoxymannojirimycin, l,4-dideoxy-l,4-imino-D-arahinitol, and fagomine. J. Am. Chem. Soc., 1989, 111, 3924. 

Both the aldol and reverse aldol reactions are encountered in carbohydrate metabolic pathways in biochemistry (see Chapter 15). In fact, one reversible transformation can be utilized in either carbohydrate biosynthesis or carbohydrate degradation, according to a cell s particular requirement. o-Fructose 1,6-diphosphate is produced during carbohydrate biosynthesis by an aldol reaction between dihydroxyacetone phosphate, which acts as the enolate anion nucleophile, and o-glyceraldehyde 3-phosphate, which acts as the carbonyl electrophile these two starting materials are also interconvertible through keto-enol tautomerism, as seen earlier (see Section 10.1). The biosynthetic reaction may be simplihed mechanistically as a standard mixed aldol reaction, where the nature of the substrates and their mode of coupling are dictated by the enzyme. The enzyme is actually called aldolase. 

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