Transglutaminase-catalyzed glycosylation of natural actomyosin (NAM) using glucosamine as amine donor: Functionality and gel microstructure

Functionality of muscle proteins is closely related to the qualitative characteristics of the final products. Enzymatic glycosylation was explored as a way to upgrade the functionality of muscle proteins, thus increasing their successful utilization by the food industry. After actomyosin was extracted from chicken muscle and reacted with glucosamine using transglutaminase, the changes in functional properties and gel microstructure of glycoconjugates were investigated. The reaction was confirmed by sequential information obtained from an Orbitrap-LC–MS and relative quantification of glucosamine-adducts in conjugated actomyosin was assessed by matrix-assisted laser desorption/ionization mass spectrometry. The highest conjugation efficiency was obtained at 37 °C and a 1:1 protein/sugar ratio in the reaction mixture. For this treatment, solubility at the isoelectric point (pI) increased from 8.7 to 34% as compared to non-treated actomyosin, probably due to the hydrophilicity conferred by glucosamine attachment. Particle size and distribution analyses revealed that enzymatic conjugation of NAM-glucosamine at 37 °C improves emulsifying activity and stability of NAM, particularly at the proteinʹs pI. Glycosylation exhibited a protective effect on actomyosin during heat-induced gelation. Cryo-electron scanning microscopy of actomyosin glycoconjugates revealed a strong effect of the level of glycosylation of the gelsʹ microstructure. In particular, a highly dense network with a more closed nature was found for the glycoconjugates produced at 37 °C. Due to their improved solubility and emulsifying properties, actomyosin glycoconjugates represents a promising new additive for the food industry.