文摘
Using 28 chemically well-defined compounds containing D-erythro-sphingosine and itsanalogues, we analyzed structure-activity relationships for DNA primase inhibition. Biochemical studiesdemonstrated a positively charged amino group at C2 and a long aliphatic chain to be absolutely requiredfor inhibition. Whereas C2-amino group is intact, sphingosine 1-phosphate was totally inactive. This resultcould be due to cancellation of positive charge of the amino group by the interaction with negativelycharged C1-phosphate, since simulations with the software INSIGHT II showed these two groups to beclose enough to interact. The hydroxyl group at C3 and trans-double bond at C4-C5 were also found tobe important for the inhibition. Dehydroxylation of C3, as well as saturation or cis-conversion of thetrans-double bond led to decrease of inhibitory activity. Despite saturation of the double bond, introductionof a hydroxyl group into C4 of dihydrosphingosine resulted in restoration of inhibition. Conversion of thedouble bond into a triple bond did not abolish but rather enhanced the inhibitory activity. Amongsphingosine stereoisomers, the naturally occurring D-erythro-sphingosine proved to be the strongest inhibitor.To ascertain the contribution of the total conformation to the inhibition, especially of the long aliphaticchain, we constructed a 3D-quantitative structure-activity relationship model using the computer program Catalyst/HipHop on the basis of information described above. Analysis of the hypothesis model foractive compounds revealed that the orientation of aliphatic chain, represented by the dihedral angle ofC2-3-4-5, correlated well with the inhibition. Modifications such as deletion of the hydroxyl group atC3 or saturation of the C4-C5 double bond caused shifts in the dihedral angle of C2-3-4-5, withconcomitant decrease in inhibitory activity.
