Application of an acid proteinase from Monascus purpureus to reduce antigenicity of bovine milk whey protein

An acid proteinase from Monascus purpureus No. 3403, MpuAP, was previously purified and some characterized in our laboratory (Agric Biol Chem 48:1637–1639, 1984). However, further information about this enzyme is lacking. In this study, we investigated MpuAP’s comprehensive substrate specificity, storage stability, and prospects for reducing antigenicity of whey proteins for application in the food industry. MpuAP hydrolyzed primarily five peptide bonds, Gln⁴–His⁵, His¹⁰–Leu¹¹, Ala¹⁴–Leu¹⁵, Gly²³–Phe²⁴ and Phe²⁴–Phe²⁵ in the oxidized insulin B-chain. The lyophilized form of the enzyme was well preserved at 30–40°C for 7 days without stabilizers. To investigate the possibility of reducing the antigenicity of the milk whey protein, enzymatic hydrolysates of the whey protein were evaluated by inhibition ELISA. Out of the three main components of whey protein, casein and α-lactalbumin were efficiently degraded by MpuAP. The sequential reaction of MpuAP and trypsin against the whey protein successfully degraded casein, α-lactalbumin and β-lactoglobulin with the highest degree of hydrolysis. As a result, the hydrolysates obtained by using the MpuAP–trypsin combination showed the lowest antigenicity compared with the single application of pepsin, trypsin or pepsin–trypsin combination. Therefore, the overall result suggested that the storage-stable MpuAP and trypsin combination will be a productive approach for making hypoallergic bovine milk whey protein hydrolysates.