objective: Chronic β-alanine supplementation leads to increased levels of muscle histidine-containing dipeptides. However, the majority of ingested β-alanine is, most likely, degraded by two transaminases: GABA-T and AGXT2. In contrast to GABA-T, the in vivo role of AGXT2 with respect to β-alanine metabolism is unknown. The purpose of the present work is to investigate if AGXT2 is functionally involved in β-alanine homeostasis. methods: Muscle histidine-containing dipeptides levels were determined in AGXT2 overexpressing or knock-out mice and in human subjects with different rs37369 genotypes which is known to affect AGXT2 activity. Further, plasma β-alanine kinetic was measured and urine was obtained from subjects with different rs37369 genotypes following ingestion of 1400 mg β-alanine. results: Overexpression of AGXT2 decreased circulating and muscle histidine-containing dipeptides (>?70% decrease; p??0.05). In humans, the results support the evidence that decreased AGXT2 activity is not associated with altered histidine-containing dipeptides levels (p?>?0.05). Additionally, following an acute dose of β-alanine, no differences in pharmacokinetic response were measured between subjects with different rs37369 genotypes (p?>?0.05). Interestingly, urinary β-alanine excretion was 103% higher in subjects associated with lower AGXT2 activity, compared to subjects associated with normal AGXT2 activity (p?