title: Covalent binding of 4-hydroxy-2-nonenal to lactate dehydrogenase decreases NADH formation and metmyoglobin reducing activity.
abstract: Lactate dehydrogenase (LDH) activity can regenerate NADH, which is a critical component in metmyoglobin reduction. However, limited research has determined the effects of lipid oxidation products on LDH activity. The overall objective of this study was to determine the effects of 4-hydroxy-2-nonenal (HNE) on LDH activity. LDH was reacted with HNE at pH 5.6 and 7.4, and LDH activity was measured as NADH formation following the addition of lactate and NAD. The effects of HNE on NADH-dependent metmyoglobin reduction also were analyzed. Mass spectrometric examination revealed that HNE adducts to LDH at both pH 5.6 and 7.4. More specifically, HNE binds with cysteine and histidine residues of LDH at pH 5.6 and 7.4. Covalent binding of HNE decreased NADH formation and metmyoglobin reduction (P < 0.05). These results indicate that secondary lipid oxidation products can inactivate enzymes involved in metmyoglobin reduction and have the potential to increase beef discoloration.
authors.affiliation: Department of Animal Science, University of Connecticut , 3636 Horsebarn Road Extension, Unit 4040, Storrs, Connecticut 06249-4040, United States.
authors.forename: Ranjith
authors.initials: R
authors.lastname: Ramanathan
authors.forename: Richard A
authors.initials: RA
authors.lastname: Mancini
authors.forename: Surendranath P
authors.initials: SP
authors.lastname: Suman
authors.forename: Carol M
authors.initials: CM
authors.lastname: Beach
mesh_terms: D000447:Aldehydes / Q000737:chemistry* / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D002417:Cattle; D007770:L-Lactate Dehydrogenase / Q000737:chemistry* / Q000378:metabolism; D013058:Mass Spectrometry; D008460:Meat / Q000032:analysis*; D008786:Metmyoglobin / Q000737:chemistry* / Q000378:metabolism; D008969:Molecular Sequence Data; D018482:Muscle, Skeletal / Q000737:chemistry* / Q000378:metabolism; D009243:NAD / Q000737:chemistry* / Q000378:metabolism; D010084:Oxidation-Reduction; D011485:Protein Binding
chemical_list: D000447:Aldehydes; D009243:NAD; D008786:Metmyoglobin; D007770:L-Lactate Dehydrogenase; C027576:4-hydroxy-2-nonenal