L-Alanine

Archives of Microbiology,1994.161:168–175.

Formation of L-alanine as a reduced end product in carbohydrate fermentation by the hyperthermophilic archaeon Pyrococcus furiosus.[Reference: WebLink]

METHODS AND RESULTS:
The hyperthermophilic archaeon Pyrococcus furiosus was found to form substantial amounts of L-Alanine during batch growth on either cellobiose, maltose or pyruvate. Acetate, CO2 and H2 were produced next to alanine. The carbon- and electron balances were complete for all three substrates. Under standard growth conditions (N2/CO2 atmosphere) an alanine/acetate ratio of about 0.3 was found for either substrate. The alanine /acetate ratio was influenced, however, by the hydrogen partial pressure. In the presence of S0 or in coculture with Methanococcus jannaschii this ratio was only 0.07, whereas under a H2/CO2 atmosphere this ratio could amount up to 0.8. Alanine formation was also aflected by the NH sup+inf4concentration, i.e. below 4 mM, NH sup+inf4becomes limiting to alanine formation. Alanine formation was shown to occur via an alanine aminotransferase, which exhibited a specific activity in cell-free extract of up to 6.0 U/mg (90°C; direction of pyruvate formation). The alanine aminotransferase probably cooperates with glutamate dehydrogenase (up to 23 U/mg; 90°C) and ferredoxin: NADP+ oxidoreductase (up to 0.7 U/mg, using methyl viologen; 90°C) to recycle the electron acceptors involved in catabolism.
CONCLUSIONS:
Thus, the existence of this unusual alanine-forming branch enables P. furiosus to adjust its fermentation, depending on the redox potential of the terminal electron acceptor.

Clinical ence, 2005, 109(5):447-55.

L-Alanine induces changes in metabolic and signal transduction gene expression in a clonal rat pancreatic beta-cell line and protects from pro-inflammatory cytokine-induced apoptosis.[Reference: WebLink]

Acute effects of nutrient stimuli on pancreatic beta-cell function are widely reported; however, the chronic effects of insulinotropic amino acids, such as L-Alanine, on pancreatic beta-cell function and integrity are unknown.
METHODS AND RESULTS:
In the present study, the effects of prolonged exposure (24 h) to the amino acid L-Alanine on insulin secretory function, gene expression and pro-inflammatory cytokine-induced apoptosis were studied using clonal BRIN-BD11 cells. Expression profiling of BRIN-BD11 cells chronically exposed to L-Alanine was performed using oligonucleotide microarray analysis. The effect of alanine, the iNOS (inducible nitric oxide synthase) inhibitor NMA (N(G)-methyl-L-arginine acetate) or the iNOS and NADPH oxidase inhibitor DPI (diphenylene iodonium) on apoptosis induced by a pro-inflammatory cytokine mix [IL-1beta (interleukin-1beta), TNF-alpha (tumour necrosis factor-alpha) and IFN-gamma (interferon-gamma)] was additionally assessed by flow cytometry. Culture for 24 h with 10 mM L-Alanine resulted in desensitization to the subsequent acute insulin stimulatory effects of L-Alanine. This was accompanied by substantial changes in gene expression of BRIN-BD11 cells. Sixty-six genes were up-regulated >1.8-fold, including many involved in cellular signalling, metabolism, gene regulation, protein synthesis, apoptosis and the cellular stress response. Subsequent functional experiments confirmed that L-Alanine provided protection of BRIN-BD11 cells from pro-inflammatory cytokine-induced apoptosis. Protection from apoptosis was mimicked by NMA or DPI suggesting L-Alanine enhances intracellular antioxidant generation.
CONCLUSIONS:
These observations indicate important long-term effects of L-Alanine in regulating gene expression, secretory function and the integrity of insulin-secreting cells. Specific amino acids may therefore play a key role in beta-cell function in vivo.