Peptidase M20 family, bacterial and archaeal aminoacyclase-1 indole-3-acetic-L-aspartic acid hydrolase (IAA-Asp hydrolase; IAAspH; IAAH; IAA amidohydrolase; EC 3.5.1.-) subfamily. IAAspH hydrolyzes indole-3-acetyl-N-aspartic acid (IAA or auxin) to indole-3-acetic acid. Genes encoding IAA-amidohydrolases were first cloned from Arabidopsis; ILR1, IAR3, ILL1 and ILL2 encode active IAA- amino acid hydrolases, and three additional amidohydrolase-like genes (ILL3, ILL5, ILL6) have been isolated. In higher plants, the growth regulator indole-3-acetic acid (IAA or auxin) is found both free and conjugated via amide bonding to a variety of amino acids and peptides, and via an ester linkage to carbohydrates. IAA-Asp conjugates are involved in homeostatic control, protection, storing and subsequent use of free IAA. IAA-Asp is also found in some plants as a unique intermediate for entering into IAA non-decarboxylative oxidative pathway. IAA amidohydrolase cleaves the amide bond between the auxin and the conjugated amino acid. Enterobacter agglomerans IAAspH has very strong enzyme activity and substrate specificity towards IAA-Asp, although its substrate affinity is weaker compared to Arabidopsis enzymes of the ILR1 gene family. Enhanced IAA-hydrolase activity has been observed during clubroot disease in Chinese cabbage.
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