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Rapid screening for deficiency of alpha 1-proteinase inhibitor
Insights
A simple plasma assay screens for alpha 1-proteinase inhibitor (alpha 1PI) deficiency. Low alpha 1PI levels in individuals with the Z allele lead to detectable elastase activity, aiding early diagnosis of familial emphysema.
Area of Science:
- Biochemistry
- Genetics
- Pulmonology
Background:
- Alpha 1-proteinase inhibitor (alpha 1PI) deficiency is a genetic disorder linked to familial emphysema.
- Individuals with the Z allele have reduced functional alpha 1PI levels.
- Early detection of alpha 1PI deficiency is crucial for managing emphysema risk.
Purpose of the Study:
- To develop a rapid screening procedure for detecting low elastase-inhibitory activity in human plasma.
- To identify individuals with potential alpha 1PI deficiency using a simple assay.
Main Methods:
- Incubation of excess porcine pancreatic elastase with human plasma.
- Monitoring for the formation of a complex between elastase and alpha 1-proteinase inhibitor.
- Assessing elastase-specific substrate hydrolysis to detect free enzyme activity.
Main Results:
- Normal plasma completely complexes elastase, resulting in a clear reaction mixture.
- Plasma from individuals with low alpha 1PI (e.g., Z allele homozygotes) cannot complex all elastase.
- Uncomplexed elastase hydrolyzes a substrate, producing a yellow color indicative of deficiency.
Conclusions:
- This assay provides a rapid and simple method for screening alpha 1PI deficiency.
- Early identification of individuals at risk for familial emphysema can be facilitated.
- The assay detects functional elastase-inhibitory capacity, correlating with alpha 1PI levels.
Abstract:
This rapid screening procedure for detection of low but functional elastase-inhibitory activity in human plasma is based on the fact that incubation of excess porcine pancreatic elastase (EC 3.4.21.36) with plasma results in formation of a complex with active alpha 1-proteinase inhibitor (alpha 1PI, also called alpha 1-antitrypsin). In normal individuals all of the elastase is complexed, leaving no free enzyme to hydrolyze the elastase substrate, and the reaction mixture remains clear. Because individuals homozygous for the Z allele have relatively low concentrations of alpha 1PI, their plasma cannot complex all of the elastase in the assay. The uncomplexed enzyme hydrolyzes the elastase-specific p-nitroanilide substrate, producing a yellow reaction mixture. Use of this simple assay for early screening of individuals for alpha 1PI deficiency may substantially decrease the number of untreated cases of familial emphysema, a disorder that develops as a result of a genetically derived proteinase-proteinase inhibitor imbalance.