Bacteria adenylates

Knowledge of the coenzyme forms of vitamin Bi2 has increased steadily. The first coenzyme of Bi2 isolated from bacteria had similarities to pseudovitamin Bi2 it contained adenylic acid instead of 5,6-dimethyl-benzimidazole, but differed in lacking cyanide and having an extra molecule of adenine which was assumed to be bound to the cobalt atom by the coordination site, often occupied by cyanide (B24). This coenzyme, adenylcobamide, was completely inactive for Ochromonas malhamensis, but active for Escherichia coli 113-3. 

The frequency of bacterial aminoglycoside resistance encountered in clinical practice has remained nearly constant over the past 2 decades. Of the three recognized mechanisms of resistance that occur in aerobic gram-negative bacteria, plasmid-mediated expression of enzymes that acetylate, adenylate, or phosphorylate the aminoglycosides is the most important. Ring one is the primary target of these enzymes. 

Some bacteria produce effects similar to those of cholera toxin in different ways. For example, among a variety of toxic proteins produced by Bacillus anthracis, the causative agent of anthrax, is an adenylate cyclase that is able to enter the host s cells.s Similarly, B. pertussis, in addition to... 

Occupied receptors for adrenaline, glucagon, ACTH, and histamine activate adenylate cyclase via Gs proteins. Other Gs proteins, which contain subunits designated aolf and which exist as a number of subtypes, mediate olfactory responses. Subunit aD is another specialized polypeptide which is located primarily in neural tissues. A variety of additional G proteins have been discovered in organisms ranging from bacteria to mammals.179 183-186 All have similar structures with 39- to 45-kDa a subunits, 35- to 36-kDa (3 subunits and 5- to 8-kDa y subunits. Whereas the a subunits are unique to each G protein, (3 and y subunits may be shared among several G proteins. These proteins appear to function with many kinds of hormone receptors and... 

The adenylate cyclases (AC) are a family of enzymes, which catalyze the synthesis of cyclic AMP (cAMP), from ATP. Cyclic AMP, a ubiquitous molecule in mammalian cells, plays a key role in controlling a vast number of biological processes, functioning as a major second messenger. The ACs are present in bacteria, where c-AMP plays a key role in the regulation of transcription in fungi, parasites and mammalian cells. The mammalians ACs (at least nine enzymes) are structurally unrelated to the bacterial ones consisting of 12 transmembrane helices and two cytoplasmic catalytic domains. They differ from each other in their... 

If phototrophic bacteria possess a dissimilatory ATP-sulfurylase, they convert APS with pyrophosphate directly to ATP and sulfate, without the help of an additional enzyme. Such an enzyme is necessary, if the organisms like Chlorobium vibrioforme f. thiosulfatophilum (Table IV) contain only the ADP-sulfurylase, because this enzyme liberates only ADP and sulfate from APS in the presence of inorganic phosphate. In this case, the organisms gain one ATP molecule from 2 molecules of ADP. This reaction is catalyzed by adenylate kinase which converts 2 ADP into 1 ATP and 1 AMP (38). 

The significance of PolyP AMP phosphotransferase in different bacteria is still in question. Therefore, in E. coli the ADP formation from PolyP by chain shortening was explained by a joint action of polyphosphate kinase and adenylate kinase, which formed a complex with the PolyP (Ishige and Noguchi, 2000) ... 

Figure 6.7 Enzymes coupling metabolism of PolyPs and nucleoside phosphates in bacteria (1) polyphosphate kinases (2) glucokinases (3) NAD kinases (4) PolyP AMP phosphotransferase (5) adenylate kinase.

Thus, in E. coli and P. aeruginosa the PolyP AMP phosphotransferase activity is a result of the joint action of adenylate kinase and polyphosphate kinases. The occurrence of PolyP AMP phosphotransferase in the above bacteria has, however, no genetic confirmation. No such activity was observed in eucaryotes, in line with the absence of polyphosphate kinase. 

Fungi and bacteria produce various phytotoxic cyclic peptides using nonribosomal peptide synthetase (NRPS).308 Similar to modular organization of PKS, NRPS consists of several modules containing condensation (C), adenylation (A), and thiolation (T) domains. 

Adenylate cyclase has been obtained in soluble form from bacteria [12,13], and can be prepared free of contaminating phosphodiesterase, ATPase (adenosine triphosphatase) and pyrophosphatase activities, but the relationship of the bacterial enzyme to the enzyme found in higher forms of life is not yet clear. The bacterial enzyme, for example, does not respond to mammalian hormones or sodium fluoride. 

Anthrax toxin is composed of three proteins protective antigen (PA 83kDa), lethal factor (LF 90kDa), and edema factor (EF 89kDa). Individually, none of the three proteins are toxic but interact synergistically with at least one of the others. PA and LF (called LeTx) can cause lethal shock in experimental animals, and a mixture of PA and EF (edema toxin, EdTx) induces edema at the site of injection. Since two discrete units of the toxin are required for its action, the term binary toxin has been used to this and other bacterial toxins. Anthrax is unique from other binary toxins in that the binary moieties (EF and LF) interact only after being secreted from the bacteria. Further, EF and LF enter the cell via a single PA protein. Assembly of the three toxin proteins is initiated when PA binds to a proteinaceous cellular receptor and is activated by a member of the furin family of cellular proteases. The exact mechanisms of internalization of the toxin moieties are subject of scientific enquiry. Inside the cellular cytoplasm, EF (a calcium and calmodulin-dependent adenylate cyclase) causes a dramatic increase in intracellular cAMP concentrations and LF acts proteolytically to cleave certain MAPK kinases. 

V. cholerae is a gram-negative baciUus sharing similar characteristics with the family Enterobacteriaceae. Most pathology of cholera results from an enterotoxin (cholera toxin) produced by the bacteria. Conditions that reduce gastric acidity, such as the use of antacids, histamine-receptor blockers, or proton pump inhibitors or infections with Helicobacter pylori, increase the risk for clinical disease. Cholera toxin stimulates adenylate cyclase, which increases intracellular cAMP and results in inhibition of sodium and chloride absorption by microvillli and promotes the secretion of chloride and water by crypt cells. The toxin likely acts along the entire intestinal tract, but most fluid loss occurs in the duodenum. The net effect of the cholera toxin is isotonic fluid secretion (primarily in the small intestine) that exceeds the absorptive capacity of the intestinal tract (primarily the colon). This results in the production of watery diarrhea with electrolyte concentrations similar to that of plasma. 

Erwinia herbicola NCIMB 12126 was obtained from the National Collection of Industrial and Marine Bacteria (Aberdeen, UK), HEPES buffer sachets and magnesium acetate were obtained from Sigma (Poole, UK), adenylate kinase assay kits were obtained from Acolyte Biomedica (Salisbury, UK), sterile tissue culture grade distilled water was obtained from Gibco (Paisley, UK), L-broth and tryptone soya agar plates were obtained from Oxoid (Basingstoke, UK). 

Strain specific lysis by bacteriophages can be used to release intracellular ATP or adenylate kinase (AK). At the 13 ISBC a paper is presented on identification of bacteria using bacteriophages. There are also several papers on bioluminescent realtime detection of nucleic acid amplification, which may be used for identification of bacteria. In these assays either pyrophosphate or AMP is converted to ATP as a measure of the amplification reaction. 

Fig. 4.2. The oxidation mechanisms of lactate by sulfate in the sulfate-reducing bacteria of Desulfovibrio genus. Circled numbers 1, lactate dehydrogenase (cytochrome c-553) 2, pyruvate-ferredoxin 2-oxidoreductase (CoA-acetylating) 3, phosphate acetyltransferase 4, acetate kinase 5, sulfate adenylyltransferase 6, adenylylsulfate reductase 7, sulfite reductase 8, adenylate kinase. ATP adenosine 5 -triphosphate is also biosynthesized by the catalysis of ATP synthase using the energy liberated by the electron transfer around this part...

Some glycosylations have been observed at C 4 in natural streptomycin analogs, yielding somewhat less active antibiotics, yet remain active against bacteria that express enzymes that phosphylate and adenylate the C3"- OH. A limited number of natural modifications occur at C2", none of which abolish activity. 

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