Acidic mammalian chitinase (AMCase) is an enzyme that selectively degrades the biopolymer chitin Several chitinase enzymes are utilized by mammals to hydrolyze chitin encountered by inhalation and ingestion AMCase is distinct from other mammalian chitinases as its activity is retained in strongly acidic conditions (pH <2 0) AMCase expression is Induced by antigen-Induced mouse models of allergic lung inflammation This protein has also been implicated in the pathogenesis of asthma although its precise role is poorly defined We describe a novel way to express and purify active murine AMCase This material retains properties observed in mouse bronchoalveolar lavage (BAL) fluid with regard to pH preference of activity and its inhibition by cyclic peptide inhibitors argifin and argadin We found that chitinase in BAL from both antigen challenged and control animals have similar properties in this regard This strongly supports the notion the same enzyme (AMCase) gives rise to chitinase activity in both challenged and unchallenged animals We also describe expression of active human AMCase The methods described in this paper provide a reliable source of recombinant AMCase that can be utilized to expand understanding of AMCase s role in regulating allergic inflammation (C) 2010 Elsevier Inc All rights reserved