D- -alanine

Although all the chiral ammo acids obtained from proteins have the l configura tion at their a carbon that should not be taken to mean that d ammo acids are unknown In fact quite a number of d ammo acids occur naturally d Alanine for example is a constituent of bacterial cell walls and d senne occurs m brain tissue The point is that D ammo acids are not constituents of proteins... 

Both pure L- and D-amino acids can be made using hydantoinase enzymes. These enzymes catalyze the stereoselective hydrolysis of racemic hydantoins such as (50) which is used for the production of D-alanine (15) (58). 

D-alanine DL-alanine hydantoin D-hydantoinase + d-A- carbamylamino acid amidohydrolas Firth, crystallopoietes ... 

D-alanine (peptides) DL-alanine (peptide) amide(s) D-amino acid arninopeptidase Ochrobactrum anthropi, Bhodococcus erythropolis 174... 

Aspartame (L-aspartyl-L-phenylalanine methyl ester [22839-47-0]) is about 200 times sweeter than sucrose. The Acceptable Daily Intake (ADI) has been estabUshed by JECFA as 40 mg/kg/day. Stmcture-taste relationship of peptides has been reviewed (223). Demand for L-phenylalanine and L-aspartic acid as the raw materials for the synthesis of aspartame has been increasing, d-Alanine is one component of a sweetener "Ahtame" (224). 

The trienomycins ate isolated from Streptomjces sp. 83-16 (43,44). The assigned stmctures (Fig. 12) were based on spectral data. Acid hydrolysis of trienomycin A yielded D-alanine (42,44). The trienomycins have no antimicrobial activity but have good antitumor activity. Trienomycin A is the most active, exhibiting good in vivo antitumor activity against sarcoma 180 and P 388 leukemia in mice (241). 

Alitame. A new group of aspartyl-dipeptide sweeteners became known to the pubHc in 1983 (95). Alitame [80863-62-3] L-aspartyl-D-alanine... 

It is mentioned in Section II, C, 1 that iV -benzoyl-D-alanine cyclizes in 100% sulfuric acid to. give an azlactone which racemizes very slowly. ... 

To prevent the formation of byproducts like L-malic add and D-alanine, die cells undergo a pH-treatment to inactive fumarase and alanine racemase. Several reactor conformations have been investigated, but a two reactor system was found to be the most effective. The flow sheet of this two reactor system is given in Figure A8.15. In the first reactor L-aspartic add is formed, which reacts in die second reactor to L-alanine. 

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