Inactivation of barley limit dextrinase inhibitor by thioredoxin-catalysed disulfide reduction.
Barley limit dextrinase (LD) that catalyses hydrolysis of α-1,6 glucosidic linkages in starch-derived dextrins is inhibited by limit dextrinase inhibitor (LDI) found in mature seeds. LDI belongs to the chloroform/methanol soluble protein family (CM-protein family) and has four disulfide bridges and one glutathionylated cysteine. Here, thioredoxin is shown to progressively reduce disulfide bonds in LDI accompanied by loss of activity. A preferential reduction of the glutathionylated cysteine, as indicated by thiol quantification and molecular mass analysis using electrospray ionisation mass spectrometry, was not related to LDI inactivation. LDI reduction is proposed to cause conformational destabilisation leading to loss of function.
Enzyme and Protein Chemistry, Department of Systems Biology, Søltofts Plads Building 224, Technical University of Denmark, DK-2800 Kgs. Lyngby, Denmark.
Johanne Mørch
JM
Jensen
Per
P
Hägglund
Hans Erik Mølager
HE
Christensen
Birte
B
Svensson
D002384:Catalysis; D004220:Disulfides / Q000737:chemistry; D018525:Germination; D005978:Glutathione / Q000737:chemistry; D006026:Glycoside Hydrolases / Q000037:antagonists & inhibitors* / Q000737:chemistry; D001467:Hordeum / Q000201:enzymology*; D008958:Models, Molecular; D011487:Protein Conformation; D059748:Proteolysis; D012639:Seeds / Q000378:metabolism; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods; D013438:Sulfhydryl Compounds / Q000737:chemistry; D054480:Thioredoxin h / Q000737:chemistry; D013879:Thioredoxins / Q000737:chemistry*; D013997:Time Factors
D004220:Disulfides; D013438:Sulfhydryl Compounds; D054480:Thioredoxin h; D013879:Thioredoxins; D006026:Glycoside Hydrolases; C100181:pullulanase; D005978:Glutathione