Wide distribution of pH-dependent service of transport system ASC for both anionic and zwitterionic amino acids.

Criteria have been set up for recognizing the trait of interconvertibility of transport System ASC, whereby it operates in a deprotonated form to mediate the transport of zwitterionic amino acids and in a protonated form to transport anionic amino acids. This trait has been detected by each criterion applied, in all the tested occurrences of System ASC, as follows: the Ehrlich ascites tumor cell in suspension; a cultured variant thereof in monolayer; the Chinese hamster ovary cell CHO-K1 in monolayer; the pigeon red blood cell in suspension; and the human red blood cell in suspension. We conclude that this trait is a general feature of System ASC which may we may use provisionally in defining the system.