Modification of glutamine and lysine residues in holo and apo alpha-lactalbumin with microbial transglutaminase.
The molecular structures determine the physical properties of milk proteins and are important for the texture of many dairy-based foods. Bovine alpha-lactalbumin (alpha-LA) is a globular 123 amino acid Ca(2+) binding milk protein. Modification with microbial Ca(2+) independent transglutaminase (MTGase) was used to modify lysines and glutamines in holo and apo alpha-LA. At 30 degrees C no lysines or glutamines are modified in holo alpha-LA, whereas in apo alpha-LA lysines 13, 16, 108, and 114, and glutamines 39 and 43, are modified. At 50 degrees C lysines 13, 16, 108, and 114, but no glutamines, are modified in holo alpha-LA, whereas in apo alpha-LA lysines 5, 13, 16, 108, and 114, and glutamines 39, 43, 54, 65, and 117, are modified. The methods presented here offer the possibility to manipulate the availabilities of residues in alpha-LA to the MTGase reaction and enable the preparation of alpha-LA species with different degrees of modification and hence with different physical properties.
Nieuwenhuizen
Willem F
WF
TNO Nutrition and Food Research, Innovative Ingredients and Products, P.O. Box 360, NL-3700 AJ Zeist, The Netherlands. nieuwenhuizen@voeding.tno.nl
Dekker
Henk L
HL
de Koning
Leo J
LJ
Gröneveld
Toos
T
de Koster
Chris G
CG
de Jong
Govardus A H
GA
D000818:Animals; D002118:Calcium / Q000494:pharmacology; D002417:Cattle; D002942:Circular Dichroism; D005973:Glutamine / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D007768:Lactalbumin / Q000737:chemistry* / Q000378:metabolism; D008239:Lysine / Q000378:metabolism*; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D013306:Streptomycetaceae / Q000201:enzymology; D013379:Substrate Specificity; D011503:Transglutaminases / Q000378:metabolism*
D005973:Glutamine; D007768:Lactalbumin; D011503:Transglutaminases; D008239:Lysine; D002118:Calcium