Na(+)/H(+) antiporter that promotes normal di- or tripeptide transporter function, recovery following the peptide-induced acidification of the intestinal cytoplasm and maintenance of the peptide-dependent intestinal pH homeostasis. Regulator of free fatty acid uptake from the diet together with the dipeptide transporter pept-1. May play a timekeeper role in defecation cycle but is not necessary for pbo-4-dependent proton release. May play a role in the regulation of lifespan independent of the stress response pathway