ANALOGS OF OTHER VITAMINS 587 



Mcllwain (1945) found that pantothenate analogs, such as pantoyltaurine, 

 do not displace bound pantothenate from bacterial cells, and concluded 

 that these analogs are bacteriostatic because they block the formation of 

 the metabolically active form of pantothenate (which was not known at 

 that time). Furthermore, as Martin et al. (1950) showed, the analogs in gen- 

 eral do not interfere in the reactions involving CoA. Pantoyltaurine and 

 other analogs do not inhibit brain choline acetylase, even at concentrations 

 around 5 vaM. One analog, salicyloyl-/?-alanide, does inhibit this enzyme 

 (20% at 0.47 mM and 100% at 4.7 mM), but since neither pantothenate 

 nor CoA reverses this inhibition it is doubtful if it is specific. Most effective 

 analogs thus seem to block the pathway of pantothenate -^ CoA, and no 

 known direct antagonists of CoA are known. Pantoylaminoethanethiol in- 

 hibits the synthesis of CoA from pantetheine (50% at a ratio of analog to 

 pantetheine of 13) and thus inhibits sulfonamide acetylation in liver ex- 

 tracts provided with pantetheine (Boxer et al., 1955). One cannot help but 

 wonder in some of these instances if abnormal CoA analogs are formed, 



CH, 

 I 

 HOCH,— C— CHOH— CONH— CH,CH,— COO' 



"■ I 

 CH3 



Pantothenate 



CH3 



I 



HOCH2— C— CHOH— CONH - CHoCH,— SO: 



I - 2 3 



CH, 



Pantoyltaurine 



CH3 

 I 

 HOCH2— C-CHOH-CONH-CH2CHi-CONH-CH2CH2SH 



CH3 



Pantetheine 



CH, 



I 



OH 



HOCH2—C — CHOH— CONH- CH2CH2SH / A— CONH-CH2CH2— COO" 

 CH3 \ / 



Pantoylaminoethanethiol Salicyloyl-/3-alanide 



