Stickland reactions

FIGURE 7.26 Stickland reaction between L-proline and L-alanine. 

Naumann E, H Hippe, G Gottschalk (1983) Betaine new oxidant in the Stickland reaction and methanogen-esis from betaine and L-alanine by a Clostridium sporogenes-Methanosarcina barkeri coculture. Appl Environ Microbiol 45 474-483. 

Once identified as a selenoprotein in this model (C. sticklandii), the need for selenium was also shown for C. sporogenes The addition of selenium to the culture medium was reported to improve the level of D-proline reductase activity as early as 1976, ° yet the first identification of the selenoprotein component of this enzyme did not occur until more recentiy in 1999 by Andreesen s group. It is quite clear now from data from these model systems, as well as from DNA sequence analysis of the grd aiiAprd operons, ° ° that Stickland reactions are common to many amino acid-fermenting clostridia. Those that are capable of proline reduction all... 

Betaine is a fermented strain of Desulfuromonas acetoxidans with the production of trimethylamine and acetate (Heijthuijsen and Hansen 1989b), and the same products are formed by Clostridium sporogenes in a Stickland reaction with alanine, valine, leucine, or isoleudne (Naumann et al. 1983). 

Dismutation—the Stickland reaction between pairs of amino acids (Section 6.7.1)... 

The Stickland reaction (47) has received much attention as a possible route to chiral acetate due to the availability of chiral glycine (48). In the Stickland reaction two moles of glycine and one mole of d-alanine are converted quantitatively into three moles of acetate, three moles of ammonia, and one mole of C02 by the organism Clostridium sticklandii. The presence of amino acid transaminase in the intact organisms leads to extensive hydrogen exchange although in the purified enzyme the replacement of NH2 by H occurs stereospecifically with inversion (49, 50). Unfortunately, the rates of conversion with the purified enzyme are too low to be synthetically useful. 

These reactions were first described by Stickland and this d-amino acid may account for up to 25% of the total amino acids in plaque fluid. Stickland reactions are usually associated with amino acid-fermenting anaerobic organisms which are commonly found in the region of the gingival crevice and in periodontal pockets. Tissue destruction and proteolytic activity in this region would generate an excess of free amino acids thus favouring 5-aminopentanoic acid accumulation. 

C. sporogenes can produce acetic, propionic, butyric, isovaleric, isobutyric and isocaproic acid, hydrogen and carbon dioxide. By the current state of scientific knowledge, C. sporogenes produces the carboxylic acids applying the Stickland reaction. This reaction is a particular kind of fermentation of amino acids which is characterised by simultaneous oxidation of one amino acid and reduction of another... 

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