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A pentose sugar, also known as d -riboketose and d -erythropetulose; it has never been prepared in crystalline form, and exists only as a syrup. The structural formula of ribulose is shown below.

Ribulose-5-phosphate occurs in animal and plant tissues. It can be converted to ribulose-l, 5-diphosphate by a phosphokinase enzyme acting in the presence of adenosine triphosphate (ATP). The ribulose-5-phosphate is also a significant intermediate in the carbohydrate metabolism through the pentose phosphate pathway. See Carbohydrate metabolism, Monosaccharide

McGraw-Hill Concise Encyclopedia of Bioscience. © 2002 by The McGraw-Hill Companies, Inc.
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.



(also D-erythropetulose), a monosaccharide belonging to the pentose (ketopentose) group. The esters of ribulose and phosphoric acid, namely, ribulose-5-phosphate and ribulose-1, 5-diphosphate, participate in important metabolic processes involving the breakdown of carbohydrates (pentose phosphate cycle), as well as in the production of carbohydrates in green plants during photosynthesis. Ribulose can be obtained either by the action of alkalis on arabinose or from formaldehyde in the presence of CaCO3.

The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.


C5H10O5 A pentose sugar that exists only as a syrup; synthesized from arabinose by isomerization with pyridine; important in carbohydrate metabolism. Also known asD-erythropentose;D-riboketose.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
References in periodicals archive ?
It was also observed that the restriction of the gas exchange activity was so drastic that the reduction of the photosynthetic activity in the higher levels of salinity promoted an increase of the internal [CO.sub.2] concentration, as observed in the [A.sub.3] management plants, probably due to the malfunction of the activity of the enzyme Ribulose 1,5-bisphosphate carboxylase oxygenase (RuBisCO) (Fugura 7D).
Rubisco (ribulose 1,5-bisphosphate carboxylase/oxygenase), the most abundant enzyme in nature and responsible for C[O.sub.2] fixation by photosynthetic organisms, is a complex protein composed from eight identical large subunits ([M.sub.r] 53000) that are encoded in the chloroplast genome, each one with catalytic site and eight identical small subunits ([M.sub.r] 14000) that are encoded in the nuclear genome [64].
In maize, two distinct ribulose 1,5-bisphosphate carboxylase/ oxygenaseactivase transcripts have different day/night patterns of expression.
[28.] Goloubinoff P, Christeller JT, Gatenby AA, Lorimer GH Reconstitution of active dimeric ribulose bisphosphate carboxylase from an unfoleded state depends on two chaperonin proteins and Mg-ATP.
TABLE 1: Expression of Symbiodinium ribulose, 1-5, bisphosphate carboxylase/oxygenase large subunit (rbcL), photosy Gene Function Results from prior Results discussed works herein rbcL Photosynthesis Higher at variable temperature (a) psI Photosynthesis Higher at variable Negatively correlated temperature (a) with [F.sub.v]/ Higher [F.sub.M.sup.b] pgpase Photosynthesis Higher at variable Positively correlated temperature (a) with ps1 (b) apxl Stress response Positively correlated with pgpase (b) (a) See [4].
The effect of ethylene on photosynthesis also has influence on plant water use efficiency and associated with higher Rubisco (ribulose 1,5 bisphosphate carboxylase) activity or rate of electron transport (Van den Boogard et al., 1996).
The oxidative branch of the PPP converts glucose into ribulose and generates the reducing force NADPH, which is critical in defense against oxidative stress, lipid synthesis, and many other anabolic reactions.
Rubisco large subunit: The large subunit (53kDa) of Ribulose 1,5-bis phosphate carboxylase/oxygenase that functions in the dark reaction of photosynthesis is the most abundant protein.
Results: Proteins of plant origin in Ankaferd[R] were NADP-dependent-malic enzyme, ribulose bisphosphate-carboxylase-large chain, maturase K, ATP synthase subunit-beta, ATP synthase subunit-alpha, chalcone-flavanone isomerase-1, chalcone-flavanone isomerase-2, and actin-depolymerizing factor.
As shown in Figure 7-3, C[O.sub.2] is added to a five-carbon compound called ribulose diphosphate (RuBP).