THE EFFECT OF ACYLATED POLYAMINE DERIVATIVES ON POLYAMINE UPTAKE MECHANISM, CELL-GROWTH, AND POLYAMINE POOLS IN ESCHERICHIA-COLI, AND THE PURSUIT OF STRUCTURE ACTIVITY RELATIONSHIPS/

Two acetyl analogues of spermidine and five analogues of spermine were used to determine the structural specificity of the polyamine transpo rt system in Escherichia coli by measuring their ability to compete wi th [C-14]putrescine or [C-14]spermine for uptake, as well as to inhibi t cell growth, and, finally, to affect the intracellular polyamine poo ls. Spermine uptake follows simple Michaelis-Menten kinetics (K-i = 24 .58 +/- 2.24 mu M). In contrast, the putrescine uptake system involves two saturable Michaelis-Menten carriers exhibiting different affinity towards putrescine (K-i = 3.63 +/- 0.43 mu M, K-i' = 0.61 +/- 0.10 mu M). From the K-i values, it is inferred that N-1-5-amino-3-nitrobenzo ylspermine is the most effective competitive inhibitor followed by N-1 -acetylspermine, and then N-1,N1(12)-diacetylspermine. N-1-acetylsperm idine and N-8-acelylspermidine also inhibit competitively the uptake o f spermine, the latter being the most effective inhibitor. In addition , the above-mentioned analogues inhibit identically one of the carrier s of putrescine uptake, suggesting the existence of a common transport er for both putrescine and spermine. The order of analogue potency reg arding the other carrier of putrescine is as follows: N-1,N-12-diacety lspermine congruent to N-1-5-amino-2-nitro-benzoylspermine > N-1-acety lspermine. Both N-1-acetylspermidine (k(i) = 753 +/- 25 mu M, K-i' = 1 28 +/- 5 mu M) and N-8-acetylspermidine (K-i = 22.4 +/- 0.4 mu M, K-i' = 279 +/- 3 mu M) also cause competitive inhibition of putrescine upt ake, however with inverse affinity towards the putrescine carriers. Ne ither N-4,N-9-diacetylspermine, nor N-1,N-4-bis(beta-alanyl)diaminobut ane affect the uptake of any polyamine. Interestingly, none of the ace tyl analogues of spermine has a mensurable effect on cell growth and c ellular polyamine pools. although some of them are accumulated in cell s, Based on these findings, the relative significance of the primary a nd secondary amines and of the chain flexibility as determinants of ce llular uptake are discussed.