RESUMEN
Objective To establish the synthetic method of the substrate for angiotensin-converting enzyme(ACE),and investigate the assay method of sernm ACE. Methods The substrate was prepared by the use of N-hydroxysuccinimide ester in peptide synthesis,and serum ACE was determined by spectrophotometric assay using suhstrate. Results The substrate of furanacryloyl-phenylalanyl-glycyl-glycine with purity of 99.5% was obtained.The K_m value for the substrate was 0.25 mmol/L,the normal reference interval for serum ACE activity was 46.7 U/L to 113.3 U/L,and the within-run and between-run coefficient of variation(CVs)ranged from 3.9 to 4.9%.The serum ACE activity in patients with squamous carcinoma and adenocarcinoma of lung were significantly decreased(P<0.05),while that in patients with lung small cell carcinoma was not significantly decreased(P>0.05). Conclusion The synthesized substrate could be reliably used as a marker for diagnosis of different lung cancers in clinics.