Gelation mechanism of protein solution by transglutaminase.

Abstract

Transglutaminasecatalyzes the formation of £-(y-glutamyl)lysyl cross-links within and between protein molecules. Therefore, transglutaminase polymerizes proteins through the formation of isopeptide bonds. Wehave reported that several high-concentration protein solutions formed firm gels when they were incubated with transglutaminase. This paper presents unambiguous evidence that asl-casein solution is gelled by the formation of £-(y-glutamyl)lysyl cross-links.Gelation of asl-casein was effected by the amount of transglutaminase and pHvalue, and asl-casein gel was not dissolved by various denaturants. Succinylated asl-casein, in which e-amino groups of lysine residues are blocked, was not gelled by transglutaminase. Therefore, it is confirmed that <xslcasein is formed by the action of transglutaminase.It has been recognized that intramolecular disulfide bonds play an important role in the protein structure.1} In addition, much attention has been paid from the physiological aspect to other covalent cross-links within and between protein molecules. There are two types that comprise these cross-links. One type, which occurs in collagen2) and elastin,3)is the Shiff bases formed by the condensation between lysine-and hydrolysine-derived aldehyde and 8-amino groups of protein-bound Lys residues. The other type is e-(yglutamyl)lysyl cross-links which occur in fibrin clot4) and epidermal keratinocytes.5) It is known that cross-links of this type are formed by transglutaminase. Transglutaminase (Rglutaminyl-peptide: amine y-glutamyltransferase, EC 2.3.2.13) is a Ca2+-dependent enzyme which catalyzes the intra-and intermolecular cross-linking of certain proteins by y-glutamyle-lysine side chain bridges.6'7)

Modifications of structures and functions of caseins: a scientific and technological challenge

“…As expected, these cross-linking reactions led to modifications of functional properties of caseins such as solubility, emulsifying capacity, foaming, and gelation properties (Motoki et al 1984;Nio et al 1986;Faergemand and Qvist 1997;Nonaka et al 1997;Faergemand et al 1998;Ozer et al 2007). Cross-linking of casein micelles improved their intra-micellar stability.…”

Transglutaminaz Enziminin Tavuk Köftesinin Kalite Özelliklerine Etkisi

“…Enzim ilavesi köftelerin pişirme kayıplarında azalmaya neden olmuş ve bu azalma enzim katılmayan grup ile %1 enzim ilaveli grup arasında TGaz enzimi üzerine yapılan çalışmaların sonucunda elde edilen en önemli bulgular, ürünlerin tekstür ve jel kuvvetindeki meydana gelen artışlardır. TGaz ilavesinin, moleküller arası ε (γ-glutamil)-lisil çapraz bağlarının oluşumu yoluyla daha sıkı jel ağ yapısına neden olduğu birçok araştırmada bildirilmektedir 9,[23][24][25][26] . Araştırmamızda da bu durum net bir şekilde ortaya konmuştur.…”

Optimierung einer rekombinanten mikrobiellen Transglutaminase

“…Verschiedene Proteine industriell gefertigter Lebensmittel, wie Casein und Sojaproteine, stellen gute Substrate für tierische TGs dar. Eine Quervernetzung dieser Proteine führt zu verbesserten Eigenschaften in Bezug auf Gelierung, Löslichkeit und Emulgierfähigkeit [9,10].…”