The biochemical basis of lower metmyoglobin reducing
activity (MRA)
in high-oxygen modified atmospheric packaged (HiOx-MAP) beef than
those in vacuum and polyvinyl chloride (PVC) packaging is not clear.
To explore this, the effects of lipid oxidation products with varying
carbon chain length on lactate dehydrogenase (LDH) and NADH-dependent
metmyoglobin reductase activity were evaluated. Surface color, MRA,
and lipid oxidation of beef longissimus lumborum steaks (n = 10) were measured during 6-day display. Further, two enzymes,
LDH and NADH-dependent metmyoglobin reductase (n =
5), critical for MRA were incubated with or without (control) lipid
oxidation products of varying carbon chain length: malondialdehyde
(3-carbon), hexenal (6-carbon), and 4-hydroxynonenal (9-carbon). Steaks
in HiOx-MAP had greater (P < 0.05) redness than
vacuum and PVC, but had lower (P < 0.05) MRA and
greater (P < 0.05) lipid oxidation on day 6. LDH
and NADH-dependent metmyoglobin reductase activities were differentially
influenced by lipid oxidation products (P < 0.05).
The results indicate that the difference in reactivity of various
lipid oxidation products on LDH (HNE > MDA = hexenal) and NADH-dependent
metmyoglobin reductase (HNE = MDA > hexenal) activity could be
responsible
for lower MRA in HiOx-MAP.
The objective of the current study was to evaluate the effects of lipid peroxidation products, malondialdehyde (MDA), hexenal, and 4-hydroxynonenal (HNE), on calpain-1 function, and liquid chromatography and tandem mass spectrometry (LC-MS/MS) identification of adducts on calpain-1. Calpain-1 activity slightly increased after incubation with 100 μM MDA but not with 500 and 1000 μM MDA. However, calpain-1 activity was lowered by hexenal and HNE at 100, 500, and 1000 μM. No difference in calpain-1 autolysis was observed between the control and 1000 μM MDA. However, 1000 μM hexenal and HNE treatments slowed the calpain-1 autolysis. Adducts of MDA were detected on glutamine, arginine, lysine, histidine, and asparagine residues via Schiff base formation, while HNE adducts were detected on histidine, lysine, glutamine, and asparagine residues via Michael addition. These results are the first to demonstrate that lipid peroxidation products can impact calpain-1 activity in a concentration-dependent manner and may impact the development of meat tenderness postmortem.
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