Dual specificity kinase. Is activated by cytokines and environmental stress in vivo. Catalyzes the concomitant phosphorylation of a threonine and a tyrosine residue in the MAP kinase p38. Part of a signaling cascade that begins with the activation of the adrenergic receptor ADRA1B and leads to the activation of MAPK14. . This is the function of MAP2K3 (mitogen-activated protein kinase kinase 3, Ensembl gene identifier ENSG00000034152).