Acetaldehyde dependent aldolase DERA

A sequential aldol reaction leading to sialic acid derivatives has been also presented [59], Combination of acetaldehyde dependent aldolase (DERA) and Neu5Ac aldolase catalyzed reactions led to (R)-C-4 keto acids. In this case, however, one-pot reaction sequence was not possible due to the incompatibility of the reaction conditions for two enzymes. 

Acetaldehyde-dependent Aldolases (DERA) The group of the acetaldehyde-dependent aldolase is actually constituted of only one enzyme, the DERA. The natural substrates of this enzyme are acetaldehyde 28 and o-glycer-aldehyde-3-phosphate (Ga3P) 35 for the synthesis of 2-deoxy- o-ribose 5-phosphate 36 (Scheme 28.18). 

Type I and Type II aldolases are also present in the group of pyruvate and acetaldehyde-dependent aldolases (DERA, type I). Only the glycine- and alanine-dependent aldolases work according to a different mechanism involving the PLP cofactor. 

To date, 2-deoxy-D-ribose 5-phosphate aldolase (DERA) is the only acetaldehyde-dependent aldolase being applied in organic synthesis. Thus the stereoselectivity of DERA is significant, all known enzymes from different organisms showing the same preferences, limiting the field of application to syntheses in which specifically the DERA-catalyzed enantiomer is needed. 

Scheme 5.2. The four main groups of aldolase reactions classified by their donor substrate (1) Dihydroxyacetone phosphate (DHAP)- dependent aldolases, (2) phosphoenol pyruvate (PEP)-and pyruvate-dependent aldolases, (3) 2-deoxyribose-5-phosphate aldolase (DERA), a member of the acetaldehyde-dependent aldolases, and (4) glycine-dependent aldolases (GDA).

It is the only known member of the group of acetaldehyde-dependent aldolases. In vivo, DERA catalyzes the reversible aldol reaction of acetaldehyde and G3P. The donor substrate specificity of this enzyme is not as strict as with the other aldolases. 

Deo)y-D-ribose 5-phosphate aldolases (DERAs) belong to the class of acetaldehyde-dependent aldolases. In contrast to dihydroxyacetone phosphate (DHAP) aldolases, the donor substrate specificity is not as strict, allowing for chain elongation hy two or three carbon atoms. DERA aldolases have been successfully applied to the production of nucleosides. Horinouchi... 

In contrast to transketolase and the DHAP-dependent aldolases, deoxyribose aldolase (DERA) catalyzes the aldol reaction with the simple aldehyde, acetaldehyde. In vivo it catalyzes the formation of 2-deoxyribose-5-phosphate, the building block of DNA, from acetaldehyde and D-glyceraldehyde-3-phosphate, but in vitro it can catalyze the aldol reaction of acetaldehyde with other non-phosphorylated aldehydes. The example shown in Scheme 6.28 involves a tandem aldol reaction... 

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