Cleavage of Parathyroid Hormone to the 1-34 and 35-84 Fragments by Cathepsin D-Like Activity in Bovine Parathyroid Gland Extracts

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Abstract
A crude enzyme preparation from bovine parathyroid gland homogenates which when incubated with PTH [parathyroid hormone], cleaves the hormone into 2 major fragments. Isolation and chemical analysis has led to the identification of these peptides, the 1-34 fragment and the 35-84 fragment. Digestion of PTH was totally inhibited by the inclusion of the cathepsin D inhibitor, pepstatin, in the enzyme digest. A comparison of the digest obtained using the crude enzyme fraction vs. digestion of PTH by purified bovine cathepsin D led to the findings that the same peptide products were formed in each case. The natural 1-34 hormone fragment derived from the procedure was determined to be fully biologically active in a bone resorption system.