Bacteria amino acid composition

The nutrient sparing effect of antibiotics may result from reduction or elimination of bacteria competing for consumed and available nutrients. It is also recognized that certain bacteria synthesize vitamins (qv), amino acids (qv), or proteins that may be utilized by the host animal. Support of this mode of action is found in the observed nutritional interactions with subtherapeutic use of antibiotics in animal feeds. Protein concentration and digestibiHty, and amino acid composition of consumed proteins may all influence the magnitude of response to feeding antibiotics. Positive effects appear to be largest... 

A comparison of the mean amino acid composition of the soils with those of algae, bacteria, fungi, and yeasts showed the greatest similarity to that of bacteria. [4] This suggests, perhaps not too surprisingly, a major role for microorganisms in the synthesis in the soil of amino acids, peptides and proteins from plant and animal residues, and also explains the relatively uniform amino acid composition in different soils. 

The abnormal deposits found in the brains of CJD victims consist of an abnormal isoform of PrP. Prion protein is normally found in cells. Detailed structural studies show that normal cellular PrP (PrP ) is a soluble protein whose conformation is rich in a-helices with very little P-sheet. The PrP protein extracted from the brains of CJD victims (i.e., PrP ) is identical in primary amino acid sequence to the normal PrP (PrP ). However, PrP has a much greater content of P-sheet conformation with little a-helical structure. Thus PrP is neurotoxic because of its three-dimensional structure. When the prion protein is predominantly in an a-helical conformation it is nontoxic when the prion protein is predominantly in a P-sheet conformation, it kills neurons. The prion protein is thus made neurotoxic not by its amino acid composition but by its conformation. This concept is both fascinating and terrifying. Prion diseases are transmissible thus prions are infectious agents. However, prions are not like bacteria or viruses, or other infectious microbes—they are simply protein molecules. Prions are not microbes with cell membranes and nucleic acids they are not living things. Indeed, prions are not even infectious molecules, they are infectious molecular shapes. 

The amino acid composition of the /3-lactamases listed in Table III (2, 40, 41, 43, 45, 54, 55, 58, 62-64) underlines the similarities between preparations derived from closely related strains of bacteria, especially if the combined basic and acidic amino acid content is compared (23). The staphylococcal enzymes are remarkably rich in lysine, and the lysine-arginine content of the other gram-positive /3-lactamases is almost as high. Complete absence of cysteine appears to be characteristic (2, 55), although j3-lactamases which contain at least one cysteine residue have been reported (37, 65, 66). 

The unique Hyp residue may be important both at the molecular and higher-order structure levels in collagen. Bacteria and viruses lack prolyl hydroxylase and have no hydroxyproline in their collagen-like domains. The significant differences in their amino acid composition and sequence compared to animal collagens suggest the use of alternative stabilization strategies for the triple helix (Rasmussen et al., 2003). 

Genentech scientists chose to develop recombinant tPA by successfully cloning the nucleotide sequence for tPA into a Chinese hamster ovary cell line. As opposed to bacteria (see later discussion), this mammalian cell carried out the required glycosylation, disulfide bond formation, and proper folding of tPA in the same manner as human cells. The recombinant material was identical to the human-derived material in molecular weight, amino acid composition, sequence, immunoreactivity, and kinetic constants. 

The crystallization of bacterial ferredoxin made possible determination of the amino acid composition of ferredoxin from six anaerobic bacteria... 

The compositional studies discussed in this paper have provided some insights into the DOM cycle. For example, monomer level studies have shown that the chemical composition of HMWDOM is homogeneous in the surface ocean (Aluwihare et al, 1997 McCarthy et al, 1996). Compositional differences between the surface and deep ocean have demonstrated that polysaccharides are reactive and removed with depth (Aluwihare et al, 2002 Benner et al, 1992) furthermore, the relative abundance of amides resembhng those found in N-acetyl glucosamine also decreases with depth suggesting that these compounds are reactive and likely derived from surface ocean productivity (Aluwihare et al, 2005 Benner and Kaiser, 2003). Amino acid compositions and quantities exhibit no vertical trend and certain amino acids could have a common source throughout the ocean (McCarthy et al, 1998). D enantiomers of several amino acids are also ubiquitous in HMWDOM and indicate the presence of dissolved peptides derived from bacteria. 

For historical reasons many pharmaceutical enzymes are assayed with physiological or biopolymeric substrates (proteins, polysaccharides, bacteria, oil emulsions), which causes a number of theoretical and practical problems. The interpretation of results is difficult when natural substrates are converted into products that are substrates themselves for the next enzymatic attack. Reaction rates often depend on the position of the scissile bonds in the molecule and the chemical nature of the moieties. Hydrolysis can proceed simultaneously on various bonds at various rates. In proteolysis it is assumed that some products are liberated only after denaturation and that during the reaction course new peptide bonds become accessible for hydrolysis. In these cases the enzymatic mechanisms become exceedingly complex, kinetic parameters are apparent values, and experimental results are strongly influenced by the reaction conditions. Reproducibility problems can occur upon assaying proteinases with a limited specificity for particular casein types. Bromelain and pancreatic proteinase, FEP pharmaceutical enzyme standards, are assayed with a casein substrate. The extent of soluble peptide release is a measure of proteolytic activity. However, due to limited specificity, some proteinases release peptides with a nonrandom aromatic amino acid composition. Contamination of casein preparations with protein and of test enzyme substances with other proteinases biases the assay results. Under these conditions, relative assay methods are indicated. 

Gu X., Hewett-Emmett D., Li W.H. (1998). Directional mutational pressure alfects the amino acid composition and hydrophobicity of proteins in bacteria. Genetica 102/103 383-391. 

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