Citation:
Abstract:
Cytochrome oxidase is located at the end the electron transport system, where it catalyzes the re-oxidation of
the last cytochrome molecule in the chain. This final process results in the reduction of molecular oxygen to
water. The possible incomplete reduction of molecular oxygen leads to the production of reactive oxygen
species (ROS) or free radicals such as the superoxide anion and hydrogen peroxide which are very potent in
attacking membrane proteins, resulting in the formation of protein adduct, whose accumulation is toxic to the
cell. Endogenous cellular enzymes are available to quench the ROS and free radicals and thus eliminate the
toxic byproducts. These include superoxide dismutase and catalase which remove the superoxide free radical
and hydrogen peroxide, respectively. In this study, the hormetic properties of the cationic peptide fractions
were studied in relation to the modulation of wound healing and to the activities of cytochrome oxidase and
catalase in the hepatocytes of normal rats. The cationic peptide fractions were obtained from the seeds of
Carica papaya (PAW), Chrysophyllum albidum (AGB), Citrullus lanatus (WM), Citrus aurantium (ORG),
Thaumatococcus daniellii (TDS) using standard methods. Protein determination was done spectroscopically.
In vitro studies were carried out on liver mitochondrial and post-mitochondrial fraction, viz: cytochrome
oxidase and catalase activity assays, and using a tissue culture model for wound healing, the effects on tissue
regeneration of the cationic peptide-rich indigenous African seeds were also studied, in situ. Results showed
that the peptide extracts of Carica papaya and Citrullus lanatus seeds increased the cytochrome oxidase
activity present in the liver homogenate significantly at 605 nm while that of Thaumatococcus daniellii
significantly increased cytochrome oxidase in the mitochondrial fraction across 605 nm to 630 nm. Peptides
present in the seeds of Carica papaya, Citrullus lanatus, Thaumatococcus daniellii and Chrysophyllum
albidum were able to increase catalase activity in the mitochondrial fraction while they inhibited same in the
tissue homogenate. The peptides also enhanced rat hepatocyte wound healing to varying degrees.
Keywords: Hormesis, wound healing, catalase, cytochrome oxidase, cationic seed peptides