Benzoate synthase

E. A. Taylor, D. R. J. Palmer, and J. A. Gerlt, The lesser burden borne by o-sucdnyl-benzoate synthase an easy reaction involving a carboxylate carbon add,... 

R. Meganathan, P. C. Babbitt, and J. A. Gerlt, Unexpected divergence of enzyme function and sequence N-acyl-amino add racemase is o-sucdnyl-benzoate synthase, Biochemistry 1999, 38, 4252-4258. 

O-Succinyl-benzoate synthase (OSBS) synthase (OSBS) racemization (NAAR) identical protein racemization fortuitous Palmer, 1999... 

A thylakoid-bound enzyme-complex which consists of PAL and benzoate synthase responsible for the chain-shortening from phenylalanine to BA, has been reported in prokaryotic algae such as Anacystis nidulans [50]. Furthermore, it was found that chloroplasts and thylakoids of higher plant such as Nasturtium officinale, Astibel chinensis and Hydrangea macrophylla have the capacity to catalyze the degradation of phenylalanine to BA in vitro. This enzyme-complex is able to utilize L-phenylalanine more efficiently as a substrate than exogenously supplied CA [51]. However, such an enzyme activity has not yet been detected in tobacco. 

In two particular cases.Quercus pedunculata (Ref. 20) and Aesculus hippocastanum (Ref. 19) two PAL isoenzymes,se-parated on DEAE-cellulose columns. eathibit different regulatory properties. One isoform is sensitive to feedback by c6-C3 units, whereas the other is inhibited only by C6-C1 units. Moreover, in Quercus, the C6-C3 sensitive form cosediments in microsomes with enzymes of the phciyl-propanoid pathway, while the C6-C1 sensitive form is located with benzoate synthase in a heavier fraction microbodies and mitochondria (Ref. 13). Aesculus, one of the isoforms is linked in an enzyme complex with the enzyme system giving rise to benzoic acid. 

G. Alibert, R. Ranjeva and A. Boudet, Recherches sur les enzymes catalysant la formation des acides phenoliques chez Quercus ped mculata (Ehrh.). II. Localisation intracellulaire de la phenylalanine ammoniac-lyase, de la cinnamate 4-hydroxylase et de la "benzoate-synthase", Biochim. Biophys. Acta... 

Although the formation of p-aminobenzoic acid (36) (Fig. 7.12) can be explained by amination and loss of pyruvate from w<7-chorismic acid, enzyme extracts from Enterobacter aerogenes and two Streptomyces species contain p-amino-benzoate synthase and /5< -chorismate synthase activity. Kinetic data suggest that synthesis of p-aminobenzoic acid occurs from chorismic acid (Johanni et al., 1989). p-Aminobenzoic acid is important in the formation of folic acid in fungi and bacteria (Haslam, 1974). 

Other non-heme enzymes that use dioxygen are 4-methoxy-benzoate O-demethylase, extradiol catechol dioxygenases, the oxidoreductase isopenicillin N synthase, and a-keto acid-dependent enzymes (28). Moreover, the BH4-dependent glyceryl-ether monooxygenase (GEM) also appears to be dependent on nonheme iron for catalysis (see also Section I.E). 

Squalestatin SI 29 is a potent inhibitor of mammalian squalene synthase. It is produced by Phoma species, and like lovastatin, consists of two polyketide chains a main chain hexaketide and a sidechain tetraketide. Like lovastatin, both chains are methylated, but unusually for a fungal HR polyketide, the main chain is formed from a non-acetate starter unit— benzoate is incorporated at this position. 

Figure 5. The biocatalytic pathway (boxed arrows) created for microbial conversion of D-glucose into cis, cw-muconate from the perspective of the biochemical pathways from which the enzymes were recruited. Conversion of D-glucose into DHS requires transketolase (tkt) from the pentose phosphate pathway and DAHP synthase (aroF, aroG, aroH)y DHQ synthase aroB and DHQ dehydratase aroD) from the common pathway of aromatic amino acid biosynthesis. Conversion of DHS into catechol requires DHS dehydratase (aroZ, enzyme A) from hydroaromatic catabolism, protocatechuate decarboxylase aroY, enzyme B), and catechol 1,2-dioxygenase (caM, enzyme C) from the benzoate branch of the p-ketoadipate pathway. (Adapted and reproduced with permission from ref. 21.)...

Figure 3. Proposed pathways to AA precursors. A) 3,4-dihydroxybenzaldehyde (3,4-DHBA) biosynthesis depicting the two possible routes from/ -coumaric acid to form 3,4-DHBA the oxidative ferulate and the non-oxidative benzoate pathways B) Tyramine biosynthesis. Arrows without labeling reflect chemical reactions that have not been enzymatically characterized. Enzymes that have been cloned, characterized and identified are labeled in black bold. Enzyme abbreviations PAL, phenylalanine ammonia -lyase C4H, cinnamate 4-hydroxylase C3H, coumarate 3-hydroxylase HBS, 4-hydroxybenzaldehyde synthase TYDC, tyrosine decarboxylase.

Thylakoid membranes containing phenylalanine ammonia-lyase and cinnamate 2-monooxygenase (D 22.2.1, D 22.2.2) Mitochondrial membranes containing benzoate synthetase system (D 22.2.5) Chalcone synthase (D 22.3.3)... 

Macrophomate synthase enzyme (MPHS), isolated from the fungus Macrophoma com-melinae, catalyzes the Diels-Alder cycloaddition between 2-pyrones 42 and decarboxylated oxalacetic acid 43 in aqueous buffered medium at pH 7.0, giving the benzoates 44 (Scheme 5.11). These types of aromatic compounds are commonlybiosynthesized by either a shiki-mate or polyketide pathway and therefore the reaction depicted in Scheme 5.11 supports the fact that the Diels-Alder reaction takes place in biosynthesis. 

The marine bacterium Streptomyces maritimus has been the source of an appreciable number of metabolites with various structures, among them the wailupemycins, two of which are shown in Scheme 2.31. The available experimental data suggest that the stractures of such metabolites are assembled by a type II PKS [90], a class of synthase that also works in the iterative mode. A benzoate is used as the starter unit and seven malonates are the extender units, one of them becoming subsequently reduced, but the intimate details of the whole process are not yet completely estabUshed. 

---