L-Arabinose metabolism

Kawaguchi, H., Sasaki, M., Vertes, A.A, Inui, M., and Yukawa, H. (2008) Engineering of an L-arabinose metabolic pathway in Corynebacterium glutamicum. Appl. Microbiol Biotechnol,... 

Fig. 1) [1-4]. Genes araA, araB, and araD are the structural genes for L-arabinose isomerase [5], L-ribulokinase [5], and L-ribulose 5-phosphate 4-epimerase, respectively, the first three enzymes involved in L-arabinose metabolism. These genes, together with their controlling sites,... 

For the sake of simplicity we shall assume that the era/site is a highly specialized promoter site, that is, the site for RNA polymerase attachment, and initiation of mRNA synthesis, the activator functional site, and that it includes the binding site for the cyclic AMP-activated CAP. AraO is the site on the DNA for repressor attachment. The efficiency of transcription of the operon is therefore dependent upon the concentration of (1) cyclic AMP (which is controlled by accumulated intermediates in L-arabinose metabolism through their effect on cyclic AMP synthesis... 

Sedlak, M., and Ho, N. W. Y., Expression of E. coli araBAD operon encoding enzymes for metabolizing L-arabinose in Saccharomyces cerevisiae. Enzyme Microbial Technology 2001, 28 (1), 16-24. 

There are three known metabolic pathways to 3-deoxyulosonic acids. In the first, aldonic acids, formed by oxidation of aldopyranoses to the corresponding lactones, are dehydrated to the ulosonic acids (see Fig. 6). Thus, D-arabinose is converted by way of D-arabinonic acid to 3-deoxy-o-ffZj/cero-pentulosonic acid. The latter is then subjected to oxidative cleavage, yielding pyruvic and glycolic acids. L-Arabinose is oxidized and dehydrated to the 3-deoxy-L-g Z2/cero-pentulosonic acid, which is further oxidized to... 

Xylitol is the probable connecting point between the D-xylose and L-arabi-nose metabolic pathways (Fig. 5). L-arabinose is the form found most abundantly in nature. Early work by Chaing and Knight showed that cell-free extracts of Penicillium chrysogenum convert L-arabinose to both L-ribose and L-xylulose through the intermediate, L-arabinitol (= L-arabitol) [80]. Only one enzyme, aldose reductase, appears to be responsible for the conversion of L-arabinose to L-arabinitol. Aldose reductase also acts on D-arabinose to produce D-arabitol. Witterveen et al. obtained a mutant of Aspergillus niger deficient in... 

First, we obtained three E. coli mutant strains and each strain contained a mutation in one of the three genes encoding the synthesis of the three enzymes required for metabolism of L-Arabinose in E. coli. As a results, these three mutant strains could only produce white colonies but not red colonies on MacConkey agar plates [32]. If a functional gene had been cloned into each of these mutants and could complement the specific mutation of the mutant strains, the recombinant strains should then produce red colonies on the MacConkey plates. 

A wide range of bacterial species utilizes D-xylose and L-arabinose as carbon and energy sources. In most cases, the direct isomerization of aldopentoses to their corresponding ketoses is the first step in pentose metabolism. For example, D-xylose is converted into D-xylulose and L-arabinose is converted into L-ribulose L-ribulose can be converted into D-xylulose by epimerase. D-Xylulose is the key intermediate for further metabolism. For this reason, most bacterial species can also readily utilize L-arabinose. 

Monosaccharides. M. are linear polyhydroxyalde-hydes (aldoses) or polyhydroxyketones (ketoses). Most important among M. are the pentoses (CjHiqO,) and hexoses (C6H,20 ). Important aldopentoses include, e.g., D- ribose, D- xylose, and L- arabinose. Important aldohexoses include D- glucose, D- man-nose, and D- galactose the major ketohexoses are D- fructose and sorbose. The 6- deoxy sugars L- fu-cose and L- L-rhamnose are also widely distributed hexoses. M. with more carbon atoms (heptoses 7 carbon atoms, octoses, etc.) or less carbon atoms (trioses 3 carbon atoms) do not occur in the free form in organisms but do play a role in carbohydrate metabolism as phosphate esters tetroses (4 carbon atoms) erythrose, threose are relatively rate. 

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