Dihydroxyacetone phosphate reduction

Reduction of the acyl phosphate gives glyceraldehyde 3-phosphate, which Q undergoes keto-enol tautomerization to yield dihydroxyacetone phosphate. 

Reduction of dihydroxyacetone phosphate (DHAP) from glycolysis by glycerol 3-P dehydrogenase, an enzyme in both adipose tissue and liver... 

Glycerol 3-phosphate can arise in two ways, either (i) from glycerol, via the enzyme glycerol kinase or (ii) from dihydroxyacetone phosphate, which is produced in glycolysis, by reduction with NADH, catalysed by glycerol-3-phosphate dehydrogenase ... 

Treatment with sodium borohydride of the enzyme-substrate complex of aldolase A and dihydroxyacetone phosphate leads to formation of a covalent linkage between the protein and substrate. This and other evidence suggested a Schiff base intermediate (Eq. 13-36). When 14C-containing substrate was used, the borohydride reduction (Eq. 3-34) labeled a lysine side chain in the active site. The radioactive label was followed through the sequence determination and was found on Lys 229 in the chain of 363 amino acids.186/188 188b Tire enzyme is another (a / P)8-barrel protein and the side chain of Lys 229 projects into the interior of the barrel which opens at the C-terminal ends of the strands. The conjugate base form of another lysine,... 

It was reported by Horecker and coworkers that one class of aldolases (called Class I to distinguish it from the Class II aldolase that is metal ion-dependent) could be inhibited by the addition of borohydride reducing agent to reaction mixtures containing both enzyme and substrate129,130. It was then shown for the fructose- 1,6-bis-phosphate aldolase that the inhibition resulted from reduction of the Schiff base formed between the dihydroxyacetone phosphate substrate and the -amino group of a lysine side chain, thereby compromising the ability of the lysine to participate in subsequent turnover. 

Much is known about the catalytic mechanism of triose phosphate isomerase. TIM catalyzes the transfer of a hydrogen atom from carbon 1 to carbon 2 in converting dihydroxyacetone phosphate into glyceraldehyde 3-phosphate, an intramolecular oxidation-reduction. This isomerization of a ketose into an aldose proceeds through an enediol intermediate (Figure 16.6). 

Hence, glycerol can be converted into pyruvate or glucose in the liver, which contains the appropriate enzymes. The reverse process can take place by the reduction of dihydroxyacetone phosphate to glycerol 3-phosphate. Hydrolysis by a phosphatase then gives glycerol. Thus, glycerol and glycolytic intermediates are readily interconvertible. 

Figure 26.2. Synthesis of an Ether Phospholipid. Steps in the synthesis include (1) acylation of dihydroxyacetone phosphate by acyl CoA, (2) exchange of an alcohol for the carboxylic acid, (3) reduction by NADPH, (4) acylation by a second acyl CoA, (5) hydrolysis of the phosphate ester, and (6) transfer of a phosphocholine moiety.

With these considerations in mind, it was hypothesized [4,5,15,44,45] that the pre-diether may be formed by alkylation of a glycerol derivative, tentatively dihydroxyacetone (DHA) or dihydroxyacetone phosphate (DHAP), with geranylgeranyl-PP concomitant stereoselective reduction of the ketogroup would form the sn-2,3-geranylgeranylglycerol derivative (Figs. 10-12). s -3-Glycerophosphate (GP) or... 

NaBH4 reduction with the help of CeCl3 -7H20 to obtain threo derivatives 232 (O Scheme 61). An enzymatic route for the synthesis of L-fucose analogs modified at the non-reducing end is reported by Fessner et al. [86], Using 2-Hydroxy-2-methylpropanal 233 and dihydroxyacetone phosphate 234 as substrates, branched fucose derivative 237 has been prepared via recombinant L-fuculose 1-phosphate aldolase (FucA) and L-fucose ketol isomerase (Fuel) in E. coli (O Scheme 62). 

Phosphorylation, reduction, and tautomerization. Reaction of 3-phos-phoglycerate with ATP generates the corresponding acyl phosphate, which is reduced by NADH/H to an aldehyde, Keto-eno] tautomerization of the aldehyde gives dihydroxyacetone phosphate, the same reaction as step 5 of glycolysis (Figure 29.4). 

STEPS 6-7 Reduction yields glyceratdchyde S-phosphate, which undergoes keto-enol tautomerization to give dihydroxyacetone phosphate. 

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