Influence of temperature on secretion and functionality of lupin seed γ-conglutin

Basic 7S globulins, a group of proteins commonly found in legumes, undergo the intriguing phenomenon of release from the seeds into hot water. γ-Conglutin is a representative of this group of proteins found in lupin seeds. The physiological significance and the molecular mechanism of the selective release of γ-conglutin from lupin seeds remain unknown. Therefore, the presented study aimed to determine changes in the functionality of this protein in response to the high temperature occurring during lupin seed incubation.

It was confirmed that the main protein fraction released from the seeds during high-temperature incubation was γ-conglutin. The incubation condition favours the occurrence of this protein in a monomeric form, and the temperature used corresponds to its midpoint unfolding temperature. Subsequent analysis carried out on the γ-conglutin monomer revealed changes in its functionality after heat shock. The thermally treated protein shows a considerable increase in its interaction strength with flavonoids. Moreover, the inhibitory activity against glycoside hydrolases was enhanced when γ-conglutin monomer was exposed to specific temperatures.

The results of the present study provide a potential explanation of the physiological relevance of γ-conglutin and shed new light on a possible mechanism of its activation upon specific heat treatment. This knowledge will help characterise homologous proteins, which are commonly found in other legumes and undergo a similar heat-induced secretion phenomenon. © 2021 Society of Chemical Industry.