Question: to what class of enzymes does urease belong
[{'answer': 'metalloenzymes', 'provenance': [{'wikipedia_id': '169123', 'title': 'Urease', 'start_paragraph_id': 1, 'start_character': 248, 'end_paragraph_id': 1, 'end_character': 262, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}]