Fluorogenic Polypropionate Fragments for Detecting Stereoselective Aldolases
摘要:
A series of fluorogenic polypropionate fragments has been prepared. These undergo retroaldolization to an intermediate aldehyde that liberates the fluorescent product umbelliferone by a secondary beta-elimination reaction. leading to a >20-fold increase in fluorescence (lambda(em) = 460 +/- 20 nm, lambdaex = 360 +/- 20 nm). By applying the principle of microscopic reversibility to the reversible aldol reaction, we can use these substrates to detect stereoselective aldolases. Test substrates are available to probe the classical cases of syn- and anti-selective aldolization (11a-d), Cram/ anti-Cram-selective aldolization (10a-d), and double stereoselective aldolization (3a-h). The selectivity of aldolase antibody 38C2 for these substrates is demonstrated as an example. The assay is suitable for high-throughput screening for catalysis in microtiter plates, and therefore provides a convenient tool for the isolation of new stereoselective aldolases from catalyst libraries.
Enantioselective Fluorogenic Assay of Acetate Hydrolysis for Detecting Lipase Catalytic Antibodies
摘要:
An enantioselective fluorogenic assay for the kinetic resolution of chiral alkyl acetates is demonstrated with 7-(3-aceroxybutoxy)-2H-1-henzopyran-2-ones (R)- and (S)-4 or 7-(3-acetoxy-2-methylpropoxy)-2H-1-benzopyran-2-ones (R)-4 and (S)-6. The alcohols released by hydrolysis of these acetates are oxidized by horse-liver alcohol dehydrogenase to unstable beta-(aryloxy)carbonyl compounds: which undergo beta-elimination of the strongly fluorescent product umbelliferone (= 7-hydroxy-2H-1-benzopyran-2-one; 3) (lambda(em) = 460 +/- 20 nm, lambda(ex) = 360 +/- 20 nm). Enantioselectivities are calculated from the reaction rates for each enantiomeric acetate. For a series of representative lipases, the reactivities and enantioselectivities under preparative conditions are predicted accurately. This highly sensitive enantioselective assay detects as little as 10 mu g/ml of hydrolytic enzyme, can be carried out in 96-well microtiter plates. and is compatible with cell-cult Ire media. It is, therefore, suited for screening libraries of antibodies for enantioselective lipase catalytic antibodies.