The Unique Protein Composition of Honey Revealed by Comprehensive Proteomic Analysis: Allergens, Venom-like Proteins, Antibacterial Properties, Royal Jelly Proteins, Serine Proteases, and Their Inhibitors.

Honey is a unique natural product produced by European honeybees. Due to its high economic value, honey is considered to be well characterized chemically, and it is often discovered to be an adulterated commodity. However, this study shows that our knowledge of honey protein composition, which is of high medical and pharmaceutical importance, is incomplete. In this in-depth proteomic study of 13 honeys, we identified a number of proteins that are important for an understanding of honey properties and merit additional pharmaceutical research. Our major result is an expanded understanding of the proteins underlying honey's antimicrobial properties, such as hymenoptaecin and defensin-1, glucose dehydrogenase isoforms, venom allergens and other venom-like proteins, serine proteases and serine protease inhibitors, and a series of royal jelly proteins. In addition, we performed quantitative comparisons of all of the proteins previously known or newly identified. The honey proteins, determined using label-free nLC-MS/MS in which the same protein quantity was analyzed in one series, were found in relatively similar proportions, although eucalyptus honey differed most widely from the remaining honeys. Overall, the proteome analysis indicated that honeybees supply proteins to honey in a relatively stable ratio within each proteome, but total protein quantity can differ by approximately an order of magnitude in different honeys.