Effects of microwave treated substrate on pepsin reaction kinetics

Microwave (MW) irradiated bovine serum albumin (BSA) and bromphenol blue (BPB) complex was used as substrate for the assay of pepsin by kinetic method. Decreased reaction velocity under absorbed MW energy and constant temperature was observed.Physical chemistry 2008 : 9th international conference on fundamental and applied aspects of physical chemistry; Belgrade (Serbia); 24-28 September 200

The influence of Al3+ion on porcine pepsin activity in vitro

The in vitro effect of Al3+ ions in the concentration range 1.710-6M-8.710-3M on pepsin activity at pH 2, via kinetic parameters and its electrophoretic mobility was evaluated. Kinetic study demonstrated the existence of an activation effect of Al3+ at pH 2 on pepsin molecule. Kinetic analysis with respect to concentrations of haemoglobin showed that Al3+ ions increase the maximal velocity (Vmax) and kcat values rather than apparent affinity for substrate (KS) implying the non-competitive nature of activation which indicated that aluminium was a non-essential activator of partial non-competitive type. The values of the equilibrium constants KS and KmA for dissociation of corresponding complexes were evaluated as 0.9040.083mM and 8.560.51M, respectively. Dissociation constant KA, of activator from enzyme-activator complex calculated via kinetic and direct measurement of Al3+ binding data, as well as activation constant A50, the activator concentration that gives a rate equal to half at a saturating concentration of activator, were found to be 8.820.90M, 8.390.76M, and 8.050.48M respectively. Native PAGE electrophoresis shows the decrease in electrophoretic mobility of pepsin and confirms modification of the electric charge and conformational changes of pepsin caused by bound Al3+ on the pepsin molecule. Al3+ induced conformational changes of pepsin were verified by UV-VIS and IR spectra. Moreover, the absence of conformational changes in the haemoglobin molecule in the presence of Al3+ ions confirms that the obtained activation is a consequence of conformational changes caused only in the pepsin molecule

Inhibition of trypsin by heparin and dalteparin, a low molecular weight heparin

The interaction between trypsin, a prototype S1 serine protease, with heparin and its low molecular weight derivative dalteparin were investigated. Direct inhibition of the proteolytic activity of trypsin by heparin and dalteparin, used in concentrations typical for their clinical application, was detected. The half-maximum inhibition of the trypsin activity was achieved at 15.25±1.22 mg/mL for heparin and was estimated to be at 58.47±15.20 mg/mL for dalteparin. Kinetic analyses showed that heparin and its low molecular weight derivative dalteparin inhibited trypsin by occupation of an exosite, producing noncompetitive and mixed inhibition, respectively. Heparin as a noncompetitive inhibitor with constant of inhibition Ki1,2 = 0.151±0.019 mM and dalteparin with Ki1 = 0.202±0.030 mM and Ki2 = 0.463±0.069 mM in mixed inhibition both represent moderate inhibitors of serine protease trypsin. The obtained constants of inhibition indicate that under the clinically applied concentrations of heparin and dalteparin, trypsins and their homolog S1 serine proteases could be directly inhibited, influencing the delicate control of proteolytic reactions in homeostasis

Inhibition of trypsin by heparin and dalteparin,

a low molecular weight hepari

Thermal denaturation of pepsin at acidic media: Using DSC, MALDI-TOF MS and PAGE techniques

The thermal stability of pepsin in a strong acid medium as a function of pH has been investigated using differential scanning calorimetry (DSC), UV absorbance, polyacrylamide gel electrophoresis (PAGE) and MALDI-TOF MS methods. The two independent two-state transitions model with view of physiological function of pepsin was used for analyzing thermal denaturation curves. The transition temperature (T-m) values ranging from 305.15 to 319.15K for the first transition and from 322.15 to 349.15K for the second transition in the examined pH range implicating the higher stability at pH 4 are in good agreement with MALDI-TOF MS results. The corresponding maximum, Delta G degrees(25), was stability obtained at pH 4 with values of 65.3 kJ mol(-1). (C) 2013 Elsevier B.V. All rights reserved