| Research Abstract |
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).
The enzymatic reactions of the 4-methyl homologs, (E)-3-methylpent-3-enyl diphophate (1a) and (Z)-3methylpent-3-enyl diphophate (Ib) with geranyl diphosphate (GPP) gave 4-methyl-farnesyl diphosphates (2a and 2b), respectively. The stereochemistry of each aldehyde derived from 2a or 2b was determined by CD spectrometry to be (S)- or (R)-4-methylfarnesal, respectively.
Similarly, 1a reacted with dimethylallyl diphosphate (DMAPP) to give a mixture of (4S)-4-methylgeranyl diphospahte (3a) and (4S,8S)-4,8-dimethylfarnesyl diphosphate (4a). The Z-isomer 1b also reacted with DMAPP to give the corresponding enantiomers with (4R)- and (4R,8R)-configurations.
Reactions of the 4-ethyl homologs, (E)--3-methylhex-3-enyl diphosphate (1c) and (Z)-3-methylhex-3enyl diphosphate (1d) with GPP gave two types of
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4-ethylfarnesyl diphosphates. Reactions of 1c or 1d with DMAPP also gave two types of 4-ethylgeranyl- and 4,8- diethylfarnesyl diphosphates. Meanwhile, reaction of the 4-propyl homologs, (E)--3-methylhept-3-enyl diphosphate (1e) and (Z)-3-methylhept-3-enyl diphosphate (1f) with GPP gave two types of 4-propylfarnesyl diphosphates. Reactions of 1e or 1f with DMAPP gave only two types of the4-propylGPPs
However, neither (E)-3-methyloct-3-enyl diphosphate (1g) or (Z)-3-methyloct-3-enyl diphosphate (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.
On the other hand, in order to investigate the reactivity of the homologs of homoallylic substrates, we examined the enzymatic reactions of (E)-3-methylhex-3-enyl diphosphate or (Z)-3-methylhex-3-enyl diphosphate with FPP using the undecaprenyl diphosphate synthase (UPS) of Micrococcus luteus B-P 26. (E)-3-methylhex-3-enyl diphosphate reacted with FPP to give a chiral (4S)-(2Z,6E,10E,14E)-4-ethyl3,7,11,15-tetramethylhexadeca-2,6,10,14-tetraen-1-ol. However, the Z-isomer is not accepted as a substrate for the bacterial UPS at all. Less
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