Whiteman P, Marks C, Freese E
J Gen Microbiol. 1980 Aug;119(2):493-504. doi: 10.1099/00221287-119-2-493.
aspH mutants of Bacillus subtilis have a constitutive aspartase activity and grow well on aspartate as sole carbon source. aspH aspT mutants, which are deficient in high affinity aspartate transport as a result of the aspT mutation, grow as well as aspH mutants in medium containing high concentrations of aspartate and Na+. This Na+ effect is not due to an enhancement of aspartate transport but is the result of increased cellular metabolism. The ability to grow rapidly in sodium aspartate is induced by prior growth in the presence of Na+. In potassium aspartate, the addition of arginine, citrulline, ornithine, delta 1-pyrroline-5-carboxylase or proline instead of Na+ also allows rapid growth; but in a mutant deficient in ornithine--oxo-acid aminotransferase, only pyrroline-carboxylate or proline can replace Na+. The amino acid pool of cells growing slowly in potassium aspartate contains proline at a low concentration which increases upon addition of proline (but not Na+) to the medium. Thus, Na+ addition does not increase the synthesis of proline, but proline or pyrroline-carboxylate acts similarly to Na+ either in preventing some inhibitory effect (by aspartate or the accumulating NH4+) or in overcoming some deficiency (e.g. in further proline metabolism.
枯草芽孢杆菌的aspH突变体具有组成型天冬氨酸酶活性，并且在以天冬氨酸作为唯一碳源的培养基上生长良好。由于aspT突变而缺乏高亲和力天冬氨酸转运功能的aspH aspT突变体，在含有高浓度天冬氨酸和Na+的培养基中，其生长情况与aspH突变体相同。这种Na+效应并非由于天冬氨酸转运增强，而是细胞代谢增加的结果。在天冬氨酸钠中快速生长的能力是由之前在有Na+存在的情况下生长诱导产生的。在天冬氨酸钾中，添加精氨酸、瓜氨酸、鸟氨酸、δ1-吡咯啉-5-羧酸或脯氨酸而非Na+也能实现快速生长；但在缺乏鸟氨酸-氧代酸氨基转移酶的突变体中，只有吡咯啉羧酸或脯氨酸能够替代Na+。在天冬氨酸钾中生长缓慢的细胞的氨基酸池中含有低浓度的脯氨酸，当向培养基中添加脯氨酸（而非Na+）时，脯氨酸浓度会增加。因此，添加Na+并不会增加脯氨酸的合成，但脯氨酸或吡咯啉羧酸在防止某些抑制作用（由天冬氨酸或积累的NH4+引起）或克服某些缺陷（例如在进一步的脯氨酸代谢中）方面的作用与Na+类似。
