Determination of celiac disease-specific peptidase activity of germinated cereals

Abstract

A method to determine the celiac disease-specific peptidase activity of different germinated cereals was developed. Kernels of common wheat, spelt, emmer, einkorn, rye, and barley were germinated, lyophilized, and milled into flour and bran. The latter was extracted at pH 4.0 to obtain a solution enriched with peptidases. The synthetic α-gliadin peptide with the amino acid sequence PQPQLPYPQPQLPY (peptide IV), which has been shown to be toxic for celiac disease patients, was selected as substrate for bran peptidases. It was quantified by reversed-phase high-performance liquid chromatography on C18 silica gel. For kinetic studies, rye bran extract was incubated with peptide IV at 50 °C and pH 6.5. The peptide was degraded continuously, and only 30.2% of the original peptide was detected after 90 min. Accordingly, the bran extracts of all cereals were investigated. The incubation time was set to 60 min at 50 °C, and the degradation of peptide IV was performed at pH 4.0 and 6.5, respectively. Except for rye, peptide degradation was faster at pH 4.0 than at pH 6.5. At pH 4.0, emmer extract was most active, followed by spelt, common wheat, and einkorn extracts. The activity of rye and barley extracts was significantly lower. In conclusion, the method is easy to perform, quick, and provides reproducible results. It can be applied to other peptidase sources such as bacterial or fungal cultures to optimize peptidase preparations suitable for detoxifying gluten-containing food or for drugs to treat celiac disease.