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. Colocalizes with pept-1 along the apical membrane of the intestinal cells. Expressed uniformly in the intestinal epithelial cells. Biphasic expression pattern with high expression in the L1 and L2 larval stages and gradual decrease through adult stages. RNAi-mediated knockdown of the protein causes worms to become extremely lean and transparent. Slower progression through the larval stages, in particular the L1 and L2 stages. Increase in average life span, decreased brood size and loss of fat storage granules in the intestine leading to decreased opacity. Reduced rate of pharyngeal pumping, reduced size of proton pulses inside the cells, increased intracellular acidification, reduced uptake of fatty acids, and doubling of the defecation period. Belongs to the monovalent cation:proton antiporter 1 (CPA1) transporter (TC 2.A.36) family.