The present invention relates to a newly identified human agmatinase-like arginase, designated "25312". The invention also relates to polynucleotides encoding the agmatinase-like arginase. The invention further relates to methods using the agmatinase-like polypeptides and polynucleotides as a target for diagnosis and treatment in disorders mediated by or related to the agmatinase-like arginase. The invention further relates to drug-screening methods using the polypeptides and polynucleotides to identify agonists and antagonists for diagnosis and treatment. The invention further encompasses agonists and antagonists based on the polypeptides and polynucleotides. The invention further relates to agonists and antagonists identified by drug screening methods with the polypeptides and polynucleotides as a target.