Involved in oxygen transport from the lung to the various peripheral tissues. [Hemopressin]: Hemopressin acts as an antagonist peptide of the cannabinoid receptor CNR1 (PubMed:18077343). Hemopressin-binding efficiently blocks cannabinoid receptor CNR1 and subsequent signaling (PubMed:18077343). . This is the function of HBA2 (hemoglobin subunit alpha 2, Ensembl gene identifier ENSG00000188536).