D-Ribulose

Ketoses like aldoses exist mainly as cyclic hemiacetals In the case of d ribulose furanose forms result from addition of the C 5 hydroxyl to the carbonyl group... 

Up to this point all our attention has been directed toward aldoses, carbohydrates having an aldehyde function in their open-chain form. Aldoses are more common than ketoses, and their- role in biological processes has been more thoroughly studied. Nevertheless, a large number of ketoses are known, and several of them are pivotal intermediates in carbohydrate biosynthesis and metabolism. Examples of some ketoses include D-ribulose, L-xylulose, and /-fructose ... 

Similar to DHAP aldolases, the 3-hexulose 6-phosphate aldolase found in Methylomonas Ml 5 is highly specific for the aldol donor component D-ribulose 5-phosphate, but accepts a wide variety of aldehydes as replacement for formaldehyde as the acceptor. With propanal,... 

The trivial names D-erythrulose for D-g/ycero-tetrulose, D-ribulose for D-eryf/iro-pent-2-ulose, and D-xylulose for D-fhreo-pent-2-ulose contain stereochemical redundancy and should not be used for naming derivatives. Sedoheptulose is the accepted trivial name for D-a/rro-hept-2-uIose. 

D-Ribulose Formed in metabolic processes. Ribulose phosphate is an intermediate in pentose phosphate pathway. ... 

D-erj/photosynthesis metabolic product of yeasts and many other organisms... 

Tapia, O., Andres, J. and Safont, V. S. Theoretical study of transition structures for intramolecular hydrogen transfer in molecular models representing D-ribulose-l,s-bisphosphate. A possible molecular mechanism for the enolization step in Rubisco, J.Phys.Chem., 98 (1994), 4821-4830... 

FUNCTION RUBISCO CATALYSES TWO REACTIONS THE CARBOXYLATION OF D-RIBULOSE 1,5-BISPHOSPHATE, THE PRIMARY EVENT IN PHOTOSYNTHETIC CARBON DIOXIDE FIXATION, AS WELL AS THE OXIDATIVE FRAGMENTATION OF THE PENTOSE SUBSTRATE IN THE PHOTORESPIRATION PROCESS. BOTH REACTIONS OCCUR SIMULTANEOUSLY AND IN COMPETITION AT THE SAME ACTIVE SITE. 

CATALYTIC ACTIVITY D-RIBULOSE 1,5-BISPHOSPHATE + CO(2) = 2 3-PHOSPHO-D-GLYCERATE. 

L-Fucose isomerase catalyzes the interconversion of L-fucose to L-fuculose and o-arabinose to D-ribulose. It has neither sequence nor structural similarity with the other aldose-ketose isomerases. A crystal structure of the E. coli enzyme with an L-fucitol bound in the active site shows that the active site is located in a 20 A deep pocket, at the bottom of which is a single Mn ion. Mn is bound to Oi and O2 of L-fucitol the side chains of a monodentate Glu-337, a bidentate Asp-361 (with long bonds to both oxygens), His-528 and a water molecule. ... 

Phosphoric acid esters of the ketopentose D-ribulose (2) are intermediates in the pentose phosphate pathway (see p.l52) and in photosynthesis (see p.l28). The most widely distributed of the ketohexoses is D-fructose. In free form, it is present in fruit juices and in honey. Bound fructose is found in sucrose (B) and plant polysaccharides (e.g., inulin). 

In the presence of zinc iodide, 2-furyllithium undergoes stereoselective addition to afford the anti adduct 10 with high selectivity. This adduct can be transformed into D-ribulose through standard sequences (6). 

Arabinose isomerase [EC 5.3.1.3] catalyzes the interconversion of D-arabinose and D-ribulose. The enzyme will also utilize L-fucose and more slowly utilize L-galactose and D-altrose as substrates. L-Arabinose isomerase [EC 5.3.1.4] catalyzes the interconversion of L-arabinose and L-ribulose. 

This enzyme [EC 5.3.1.13] catalyzes the interconversion of D-arabinose 5-phosphate to D-ribulose 5-phosphate. 

This enzyme [EC 4.1.1.48] catalyzes the conversion of l-(2-carboxyphenylamino)-l-deoxy-D-ribulose 5-phos-phate to generate l-(indol-3-yl)glycerol 3-phosphate, carbon dioxide, and water. In some organisms, this enzyme is part of a multifunctional protein together with one or more components of the system for the biosynthesis of tryptophan (/.e., anthranilate synthase, anthranilate phosphoribosyltransferase, tryptophan synthase, and phosphoribosylanthranilate isomerase). 

This enzyme [EC 1.1.1.137] catalyzes the reaction of d-ribitol 5-phosphate with NAD(P)+ to produce D-ribulose 5-phosphate and NAD(P)H. 

Probably the most abundant naturally occurring catalyst, this enzyme [EC 4.1.1.39], also known as rubisco , catalyzes the reaction of D-ribulose 1,5-bisphosphate with carbon dioxide to produce two 3-phospho-D-glycerate. The enzyme can also use dioxygen as a substrate instead of carbon dioxide, producing 3-phospho-D-glycerate and 2-phosphoglycolate. 

This enzyme [EC 5.1.3.1] (also known as phosphoribu-lose epimerase, erythrose-4-phosphate epimerase, and pentose-5-phosphate 3-epimerase) catalyzes the interconversion of D-ribulose 5-phosphate and D-xylulose 5-phosphate. The enzyme can also act on D-erythrose 4-phosphate. 

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