Occurrence in microorganisms

Thiamine esters, occurrence in microorganisms, VI, 172, 173 Thiaminedisulfide pyrophosphate, coenzyme activity of, VII, 96 synthesis of, VII, 96 Thiamine pyrophosphate, see also under Cocarboxylase, VII, 86 activity, VII, 93, 100 coenzyme nature, VI, 261 VII, 88, 91, 92... 

An enzyme of widespread occurrence in microorganisms, plants, and animals catalyzes the reversible oxidative decarboxylation of 6-phosphogluconic acid to Ru-6-P and COj (equation 32) in the presence of TPN, and Mg++ or Mn++ (20,96,142,172). The enzyme has been isolated from yeast and partially purified (178,179). The reversibility of reaction (32) has been demonstrated by (o) incorpora-... 

The occurrence in some plants of secondary metabolites characterized by an 0-heterocyclic structure and exhibiting antimicrobial properties is a well-known phenomenon [2,8-10]. Among them, catechins and proanthocyanidins are two classes of compounds exhibiting antimicrobial properties towards both prokaryotic and eukaryotic microorganisms. Yet, despite the large number of studies published so far, the real potentialities and limitations given by the use of this class of molecules as antiviral or antimicrobial (antibacterial, antimycotic, antiprotozoal) agents have not been critically evaluated. The present chapter represents an overview of the re-... 

Mercury and the noble metals are found in nature in their elemental forms however, they are generally unreactive and so their occurrence in the soil solution is limited. Some elements, such as sulfur, can be reduced to their elemental state (see Figure 4.8) by soil microorganisms however, they can also easily be both oxidized and the oxidized forms reduced and so are rarely found in their elemental form in soil. 

Nothing is known about the biosynthesis of the maytansine group, the only ansamycins so far identified as being of plant origin. Their similarity to the bacterial metabolite geldanamycin has led to the hypothesis that despite their occurrence in plants, microorganisms might be involved in their production. 

Pantothenic acid is of ubiquitous occurrence in nature, where it is synthesized by most microorganisms and plants fi-om pantoic acid (D-2,4-dihydroxy-3,3-dimethylbutyric acid) derived from L-vafine, and p-alanine derived from L-aspartate. Addition of cysteamine at the C-terminal end and phosphorylation at C4 of pantoic acid forms 4 -phosphopantetheine, which serves as a covalently attached prosthetic group of acyl carrier proteins, and, when attached... 

Kerscher, R., Nlirnberg, K., Voigt, J., Schieberle, R, Grosch, W. (2000) Occurrence of 12-methyl-tridecanal in microorganisms and physiological samples isolated from beef J. Agric. Food Chem. 48, 2387-2390... 

Table 11.4-1. Occurrence of different starch hydrolyzing enzymes in microorganisms.

Besides the phenylpropanoid pathway, which includes trani-cinnamic acid (CA) as a putative intermediate, SA can also be formed along a completely different biosynthetic pathway, via isochorismate, which is directly derived from chorismate [15,16] (Fig. 1). The latter pathway is found in microorganisms and its occurrence in plants cannot yet be excluded, though in the few plants studied more extensively so far, SA seems to be derived from the phenylpropanoid pathway. 

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