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Articles by C.M. Chikezie
Total Records ( 3 ) for C.M. Chikezie
  P.C. Chikezie , A.R. Akuwudike and C.M. Chikezie
  Enzyme activity depends largely on environmental conditions such as temperature and pH. The stabilities of Polyphenol Oxidase (PPO) extracted from Solanum melongenas and Musa sapientum fruits pre-incubated in varying thermal and pH conditions were carried out. Enzyme activity was measured by spectrophotometric methods. The reaction mixture contained 3.5 mL of 0.20 M phosphate buffer (pH = 6.8), 1.0 mL of 0.75 mM catechol and 0.5 mL of enzyme solution. PPOS. melongenas and PPOM. sapientum gave different temperature and pH optima. The temperature-activity profile of PPOS. melongenas and PPOM. sapientum showed a strong positive correlation (r = 0.907363). At pH = 10.0, PPOM. sapientum activity represented 65.3% decay in enzyme activity, whereas PPOS. melongenas represented 79.3% decay in enzyme activity. PPOS. melongenas and PPOM. sapientum stability at pre-incubated temperatures of 20, 50 and 60°C and pH values of 3.5, 6.0 and 8.0 were measured. Residual activities of PPOS. melongenas and PPOM. sapientum showed a strong positive correlations under the same experimental thermal conditions, with exception at 20°C (r = 0.693375). Specifically, pre-incubation of PPOM. sapientum for t = 90 min at 60°C caused 18.4% decay in relative activity of PPOM. sapientum. At t = 90 min, pre-incubation of PPOM. sapientum, in pH = 3.5 caused decay in activity within the range of 30.8-36.1%, whereas PPOM. sapientum pre-incubated in pH = 6.0 and pH = 8.0 gave decay in activity within the range of (1.5-9.8%) and (2.7-6.5%), respectively. PPOS. melongenas and PPOM. sapientum showed relatively higher stabilities as the incubation pH tended towards alkaline conditions, whereas the two experimental temperatures (20 and 60°C) promoted destabilization.
  P.C. Chikezie , A.R. Akuwudike , C.M. Chikezie and C.O. Ibegbulem
  Largely, kinetic properties of Polyphenol Oxidase (PPO) involved the study of enzyme extracts obtained from whole fruits and vegetables. In the present study, PPO was extracted from three segments of Solanum melongenas and Musa sapientum fruits and partially purified. The specific activity of PPO was measured at each purification step to ascertain level of enzyme purity. In all cases, PPO conformed to Michaelis-Menten kinetics, showing different values of kinetics parameters. Michaelis-Menten constant for PPO (PPOKm) of S. melongenas mid-section and anterior segments showed no significant difference (p<0.05), whereas the posterior gave PPOKm = 4.6±0.49 mM (p>0.05). Maximum PPO activity (PPOVmax) was highest in the posterior segment: PPOVmax = 0.602±0.09 U. Mid-section of M. sapientum exhibited the highest Km value (PPOKm = 5.8±0.69 mM) compared with the anterior (PPOKm = 3.9±0.69 mM) (p>0.05) and posterior PPOKm = 4.9±0.11 mM segments (p<0.05). Overall, M. sapientum PPOKm values were relatively higher than those of S. melongenas. Posterior S. melongenas exhibited the highest PPOVmax = 0.602±0.09 U, whereas the lowest value was registered in the anterior segment of M. sapientum PPOVmax = 0.234±0.09 U. Substrate specificity for PPO (PPOVmax/Km) extracted from various segments of S. melongenas was in the increasing order of Mid-section > Posterior > Anterior, whereas that of M. sapientum was Mid-section > Anterior > Posterior. PPOVmax/Km between the two fruits showed strong positive correlation (r = 0.862339). Catechol was a better substrate for PPOS. melongenas than PPOM. sapientum. The experimentally observed kinetic parameters of S. melongenas and M. sapientum signified the presence of PPO isoenzymes and non-uniform distribution of PPO in the two fruits.
  P.C. Chikezie , A.R. Akuwudike and C.M. Chikezie
  In vitro studies have revealed that plant extracts interfered and altered the polymerization profile of deoxygenated sickle cell haemoglobin molecules (deoxyHbS). The present study seeks to ascertain the capacity of aqueous extract of N. tabacum to alter and interfere with polymerization of deoxyHbS molecules in vitro. Spectrophotometric method was used to measure level of sodium metabisulphite induced polymerization of deoxyHbS molecule incubated in aqueous extract of N. tabacum for 180 sec. The polymerization profile of deoxyHbS molecules of control and test samples showed increasing level of polymerization with progression of experimental time. At experimental time t>30 sec, level of polymerization of control sample ranged between 60.9±0.76-100±1.05%, whereas, the test samples ranged in the following corresponding order: (N. tabacum) = 0.8 mg 100 mL-1, 65.6±0.93-176.0±4.26%, (N. tabacum) = 1.0 mg 100 mL-1, 75.7±1.07-192.9±5.03% and (N. tabacum) = 2.0 mg 100 mL-1, 135.9±5.04-297.2±19.14%. Activation of deoxyHbS polymerization by aqueous extract of N. tabacum increased in a concentration dependent manner and duration of incubation. Specifically, at t =180 sec, (N. tabacum) = 2.0 mg 100 mL-1 caused highest level of activation of deoxyHbS polymerization (197.2±19.14%); an increase in % polymerization in a ratio of 1:4.5 (approx.) compared with (N. tabacum) = 0.8 mg 100 mL-1 at t = 30 sec. The study showed that aqueous extract of N. tabacum exacerbated polymerization of deoxyHbS molecules in a concentration and time dependent manner. Therefore, N. tabacum in the present experimental form did not exhibit therapeutic potentials for management and alleviation of sickling disorder.
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