Procaryotic organisms

Procaryotic organism Microorganisms which do NOT have an organized nucleus surrounded by a nuclear membrane. Bacteria and blue-green algae fit in this category. 

This chapter reviews recent experimental evidence of a bacterial source of sodium channel blockers, principly TTXs. These findings support the hypothesis that procaryotic organisms produce TTXs which contaminate oceanic food chains. 

Table L Procaryotic Organisms that Produce Sodium Channel Blockers...

Many coals contain extended chain (> 31 carbon atoms) hopanes and related compounds which appear to be diagenetically derived from the lipids of certain procaryotic organisms. Biologically produced hopanoids exclusively possess 173H, 213H stereochemistry. The... 

The physiological roles of ascorbic acid have not yet been described in a manner that is scientifically satisfactory. The presence of ascorbic acid in all eucaryote organisms suggests fundamental roles that are not understood. The absence of ascorbic acid in procaryote organisms suggests an unknown fundamental difference between these two classes of organisms in which ascorbic acid plays an essential role. 

One of the common surface structures of archea and bacteria are monomolecular crystalline arrays of protein subunits, called S-layers [106-109]. They constitute the outermost component of tlie cell envelope of these procaryotic organisms. S-layer subunits can be aligned in lattices with oblique, square, or hexagonal symmetry. Since S-layers are monomolecular assemblies of identical protein subunits, they exhibit pores of identical size and morphology. A group of nonclassical cell wall polymers, called secondary cell wall polymers (SCWPs), are attached noncova-lently, presumably by a lectin-type interaction, to the S-layer proteins. 

MnSODs and FeSODs from most procaryotic organisms are dimeric while MnSODs from mitochondria and some thermophilic bacteria are tetrameric [21]. However, mitochondrial MnSOD from Caenorhahditis elegans was found to be dimeric [22]. Eukaryotic MnSOD is a tetrameric protein encoded in the nucleus, synthesized in the cystosol, and imported post-translationally into the mitochondrial matrix. The 25 kDa precursor protein has a mitochondrial transit peptide that is cleaved to produce the mature 22 kDa subunit. The mature protein exists as a tetramer, each subunit containing one Mn ion. The mitochondrial MnSOD primary sequences are highly homologous to the prokaryotic Mn- and FeSOD, but has no resemblance to the CuZnSODs [23]. In MnSODs and FeSODs, the metal ions are coordinated by three His N atoms and one Asp O atom [24]. 

Apparently receptors have deep evolutionary roots since many may be traced from highly evolved animals through the phylogenetic system to the lowest procaryotic organisms. The function may well have changed through evolution but the structures are reminiscent of each other. 

B-Lactam Antibiotics. — Using cell-free preparations of eucaryotic organisms, e.g., Cephalosporium acremonium, it has very clearly been shown that the biosynthesis of penicillins involves the cyclisation of an intact molecule of the tripeptide (138) to give isopenicillin N (139) (cf. Vol. 12, p.25). Streptomyces clavuligerus is a procaryotic organism which produces 6-lactam antibiotics. A cell-free preparation of this organism has been obtained which would convert (138) into (139) ... 

In yeast and filamentous fimgi, xylose is converted to xylulose in two steps, where the first reaction is catalyzed by xylose reductase (XR) and the second by xylitol dehydrogenase, (XDH) (Fig. 1) [24]. Procaryotic organisms use a xylose isomerase (XI) to perform the conversion in one step [132]. 

The enzyme L-phenylalanine ammonia lyase has been isolated and extensively purified from potato tuber , com , the yeast Rhodotorula and the procaryotic organism Strepto-... 

Jensen et al. 265, 266) studied tripeptide cyclisation in the procaryotic organism Streptomyces clavuligerus. Using an extract of sonicated cells they found that LLD-tripeptide was converted to a penicillinase sensitive... 

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