L tyrosine decarboxylase

Owing to the fully reversible equilibrium nature of the aldol addition process, enzymes with low diastereoselectivity will typically lead to a thermodynamically controlled mixture of erythro/threo-isomers that are difficult to separate. The thermodynamic origin of poor threo/erythro selectivity has most recently been turned to an asset by the design of a diastereoselective dynamic kinetic resolution process by coupling of L-ThrA and a diastereoselective L-tyrosine decarboxylase (Figure 10.47)... 

Researchers at the University of Graz, in collaboration with scientists from DSM, have developed an elegant and novel approach to the synthesis of P-amino alcohols using two different enzymes in one pot (Scheme 2.35). For example, a threonine aldolase-catalyzed reaction was initially used, under reversible conditions, to prepare L-70 from glycine 69 and benzaldehyde 68. L-70 was then converted to (R)-71 by an irreversible decarboxylation catalyzed by L-tyrosine decarboxylase. In a second example, D/L-syn-70 was converted to (R)-71 using the two enzymes shown combined with a D-threonine aldolase in greater than 99% e. e. and 67% yield ]37, 38]. 

Scheme 2.35 Combined use of threonine aldolase and L-tyrosine decarboxylase.

L-Tyrosine decarboxylase (2 mg/ml, 0.8 ml) in 100 mM sodium acetate buffer (pH 5.5) was treated with canaline as indicated for 30 min. A unit of tyrosine decarboxylase activity is that amount of enzyme forming 1 umol CO /min. See original for additional details. 

MARQUES, I.A., BRODELRJS, P.E., Elicitor-induced L-tyrosine decarboxylase from plant cell suspension cultures I. Induction and purification. Plant Physiol., 1988,88, 47-51. 

L-Tyrosine Decarboxylase Origin Streptococcus faecalis Fluka... 

As mentioned before, one of the main drawbacks in the application of threonine aldolases is their lack of erithro/threo selectivity (kinetic limitation) and their equilibrium position (thermodynamic limitation). Recently, a tandem use of LD-threonine aldolases with low selectivity and L-amino acid decarboxylases with high selectivity has demonstrated to overcome the kinetic and thermodynamic limitations in the synthesis of phenyl serine (Steinreiber et al. 2007). Starting with benzalde-hyde and glycine, i -phenyl ethanol was obtained in 58% isolated yield and R enantiomeric excess higher than 99% by the action of L-threonine aldolase (L-TA) from Pseudomonas putida, D-threonine aldolase (D-TA) from Alcaligenes xylosoxidans and L-tyrosine decarboxylase (L-TyrDC) from Enterococcus faecalis following the scheme depicted in Fig. 6.5.17. 

Finally, Griengl s group has developed the synthesis of aromatic 1,2-amino alcohols on the basis of a bienzymatic DYKAT process. The reaction occurred between a benzaldehyde derivative and glycine in the presence of L-threonine aldolase from Pseudomonas putida and L-tyrosine decarboxylase from either Enterococcus faecalis or two genes from Enterococcus faecium. The best results were obtained for the production of (5)-octopamine (99%, ee = 81%), and (5)-noradrenaline (76%, ee = 79%), as shown in Scheme 3.64. 

Some methods to measure PLP by HPLC are complementary to enzymatic determinations of PLP. An often used enzymatic method (47) for assaying plasma PLP is based on the coenzyme dependent decarboxylation of tyrosine catalyzed by L-tyrosine decarboxylase (EC 4.1.1.25). By using a well-resolved apo-enzyme preparation, it was shown that the reaction rate is directly proportional to the amount of PLP added to the reaction mixture. Conventionally, the reaction is monitored by CO2 liberation from L-tyrosine- Ci the liberated " C02 is trapped in a potassium hydroxide solution and subsequently quantitated by liquid scintillation counting. 

Scheme 1 - Biosynthetic pathway for the formation of (S)-Norcoclauriiie. The enzymes involved in the process are 1-Phenolase 2- L-Tyrosine decarboxylase 3 - L-iyosine transaminase ...

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