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The formation of most proteins consists of two steps: the synthesis of precursor proteins and the synthesis of functional proteins. In these processes, propeptides play important roles in assisting protein folding or inhibiting its activity. As an important polypeptide chain coded by a gene sequence in lipase gene, propeptide usually functions as an intramolecular chaperone, assisting enzyme molecule folding. Meanwhile, some specific sites on propeptide such as glycosylated sites, have important effect on the activity, stability in extreme environment, methanol resistance and the substrate specificity of the lipase. Studying the mechanism of propeptide-mediated protein folding, as well as the influence of propeptide on lipases, will allow to regulate lipase by alternating the propeptide folding behavior and in turn pave new ways for protein engineering research.

Objective: To study the long-term curative effects of suture plus proximal gastric vagotomy (PGV) and suture plus triad-therapy (omeprazole, amoxycillin and flagyl taken orally) for the treatment of duodenal ulcer with acute perforation., Methods: Three hundred and twenty-nine patients with duodenal ulcer and acute perforation were treated with 2 different methods, respectively. Method A was suture plus PGV (group A, 153 cases), and method B was suture plus triad-therapy (group B, 176 cases). Follow-up was made by means of correspondence, outpatient reexamination and cooperation with local hospitals in 5 to 8 years after operation. The contents of follow-up included symptom acquisition (such as upper abdominal pain or distention, pyrosis, belch, acid regurgitation, vomiting, diarrhea and conditions of living or working), gastroscopy and Helicobacter pylori (HP) detection. The curative effects were evaluated by the Visick scale., Results: Three hundred and one patients were followed up (group A 142 and group B 159). According to the Visick scale, 97 (68.3%), 19 (13.4%), 13 (9.15%) and 13 (9.15%) patients in group A, and 31 (19.5%), 28 (17.6%), 24 (15.1%) and 76 (47.8%) in group B were classified as Visick I, II, III and IV respectively (Z = -9.818, P < 0.01). As for HP detection, there were 130 (91.5%) patients in group A and 94 (59.1%) in group B (chi(2) = 41.438, P < 0.01)., Conclusions: The long-term curative effects of suture plus PGV were superior to those of suture plus triad-therapy for duodenal ulcer with acute perforation although HP positive rate was higher in group A than in group B. HP infection is one of the etiological factors of duodenal ulcer. The increased excitability of the vagus nerve remains to play an important role in duodenal ulcer.