Molecular cloning of the α‐subunit of rat endopeptidase‐24.18 (endopeptidase‐2) and co‐localization with endopeptidase‐24.11 in rat kidney by in situ hybridization

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Abstract
Endopeptidase-24.18 (endopeptidase-2, EC 3.4.24.18, E-24.18) is a Zn-ectoenzyme of rat renal and intestinal microvillar membranes exhibiting an oligometric structure, α2-β2. The primary structure of the α-subunit of E-24.18 has been defined by molecular cloning and its expression mapped in rat kidney by in situ hybridization. A 2.9-kb cDNA coding for the α-subunit was isolated and sequenced. It had an open reading frame of 2.244 base pairs coding for a type I membrane protein of 748 amino acids. The deduced amino acid sequence showed 87% identity with that of meprin A, a mouse metallo-endopeptidase, sharing common properties with the rat enzyme, and 85% identity with the human intestinal enzyme, ‘PABA-peptide hydrolase’. Northern blot analysis revealed the α-subunit to be encoded by a single mRNA species of 3.2-kb. In situ hybridization performed on rat kidney showed a co-localization of E-24.18 with endopeptidase-24.11 in proximal tubules of juxtamedullary nephrons, suggesting that the two enzymes have similar or complementary physiological functions in kidney.