Proteolytic profiles of two isoforms of human AMBN by MMP-20 and KLK-4 proteases

Ameloblastin is a protein in biomineralization of tooth enamel, however recent results indicate that this is probably not its only role in an organism. Enamel matrix formation represents a complex process enabled via specific crosslinking of two proteins – the most abundant amelogenin and the ameloblastin (AMBN). It has been described that AMBN moleculesin vitroassemble into oligomers via a sequence encoded by exon 5. Enamel is formed by the processing of enamel proteins by two specific proteases - enamelysin (MMP-20) and kallikrein 4 (KLK-4). The scaffold made of AMEL and non-amelogenin proteins is cleaved and removed from the developed tooth enamel. The human AMBN is expressed in two isoforms (ISO I and II), which probably determine different utilization dictated by their different proteolytic profiles. In this study, we compared proteolytic profiles of both isoforms of human AMBN after proteolysis by MMP-20, KLK-4, and their 1:2 mixture. Proteolysis products were analysed and cleavage sites were identified by mass spectrometry. The proteolytic profiles of two AMBN isoforms show notable differences resulting presumably in different functions of the products. Our results may help to understand the distinct role of AMBN isoforms in the human signalling pathways and utilization of the cleavage products.&nbsp