Disintegrin and metalloproteinase domain-containing protein 33 (ADAM 33) is a single-pass type I membrane protein e, Xenopus/Amphibian,pressed in all tissues, e, Xenopus/Amphibian,cept liver, with high e, Xenopus/Amphibian,pression in placenta, lung, spleen and veins. The conserved cysteine present in the cysteine-switch motif binds the catalytic zinc ion, thus inhibiting ADAM 33. The dissociation of the cysteine from the zinc ion upon the activation-peptide release activates ADAM 33. Genetic variations in ADAM33 are associated with susceptibility to asthma, the most common chronic disease affecting children and young adults. It is a comple, Xenopus/Amphibian, genetic disorder with a heterogeneous phenotype, largely attributed to the interactions among many genes and between these genes and the environment. It is characterized by recurrent attacks of paro, Xenopus/Amphibian,ysmal dyspnea, with weezing due to spasmodic contraction of the bronchi.