The most common post-translational modification of peptide hormones, present in half of all neuroendocrine (NE) peptides, is alpha-amidation and this is necessary for the biological activity of the peptides. Peptides are alpha-amidated by the action of two enzymes: peptidylglycine alpha-hydroxylating monooxygenase (PHM) and peptidylamidoglycolate lyase (PAL). As the common pathway for the formation of amidated peptides, the enzymes may provide a better indication of the NE status of a tumour or tissue than the presence of any single amidated peptide. PHM and PAL enzyme activities were measured in 39 BL fluid specimens from patients undergoing bronchoscopy for diagnosis of lung cancer. The assays revealed that PHM levels were higher in a group of specimens from patients undergoing bronchoscopy for chest infection, inflammation, asthma, or pneumonia compared to a group of specimens in which malignant cells were seen. The presence of elevated levels of amidating enzymes in specimens with non-cancerous conditions may reflect events of promotional phase cancer biology occurring simultaneously with inflammatory and infectious processes.

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