Substrate specificity of thermostable farnesyl diphosphate synthase with respect to 4-alkyl group homologs of isopentenyl diphosphate

In order to investigate substrate spcificity of Bacillus stearothermophilus farnesyl diphosphate synthase (FPS), we examined the reactivity of 4-alkyl group homologs of isopentenyl diphosphate (IPP). zymatic reactions of the 4-methyl homologs, (E)-3-methylpent-3-enyl diphophates (1a) and (Z)-3-methylpent-3-enyl diphophates (1b) with geranyl diphosphate (GPP) gave 4-methylfarnesyl diphosphates (2a and 2b), respectively. The stereochemistry of each aldehyde derived from 2a or 2b was determined by CD spectrometry to be (S)-4-methylfarnesal or (R)-4-methylfarnesal, respectively. Similarly, 1a reacted with dimethylallyl diphosphate (DMAPP) to give a mixture of (4S)-4-methylgeranyl diphosphates (3a) and (4S,8S)-4,8-dimethylfarnesyl diphosphates (4a). The (Z)-isomer 1b also reacted with DMAPP to give the corresponding enantiomers with (4R)- and (4R,8R)-configurations. other hand, reactions of the 4-ethyl homologs, (E)-3-methylhex-3-enyl diphosphates (1c) and (Z)-3-methylhex-3-enyl diphosphates (1d) with GPP gave two types of 4-ethylfarnesyl diphosphates. Reactions of 1c or 1d with DMAPP also gave two types of 4-ethylgeranyl- and 4,8-diethylfarnesyl diphosphates. ile, reaction of the 4-propyl homologs, (E)-3-methylhept-3-enyl diphosphates (1e) and (Z)-3-methylhept-3-enyl diphosphates (1f) with GPP gave two types of 4-propylfarnesyl diphosphates. Reactions of 1e or 1f with DMAPP gave only two types of the 4-propyl GPPs. r, neither (E)-3-methyloct-3-enyl diphosphates (1g) or (Z)-3-methyloct-3-enyl diphosphates (1h), nor (E)-4-bromo-3-methylbut-3-enyl diphosphate (1i) or (Z)-4-bromo-3-methylbut-3-enyl diphosphate (1j) was acceptable as a substrate for the thermophilic FPS at all.