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Kinetics and thermodynamics of a novel endoglucanase (CMCase) from Gymnoascella citrina produced under solid-state condition
Jabbar, A.; Rashid, M.H.; Javed, M.R.; Perveen, R.; Malana, M.A. (2008). Kinetics and thermodynamics of a novel endoglucanase (CMCase) from Gymnoascella citrina produced under solid-state condition. Journal of Industrial Microbiology & Biotechnology 35(6): 515-524. https://hdl.handle.net/10.1007/s10295-008-0310-4
In: Journal of Industrial Microbiology & Biotechnology. SPRINGER HEIDELBERG: Heidelberg. ISSN 1367-5435; e-ISSN 1476-5535, more
Peer reviewed article  

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Author keywords
    Endoglucanase, Activation energy, Enthalpy, Entropy, Gibbs free energy

Authors  Top 
  • Jabbar, A.
  • Rashid, M.H.
  • Javed, M.R.
  • Perveen, R.
  • Malana, M.A.

Abstract
    Gymnoascella citrina produced two isoforms of endoglucanases (CMCase-I and -ІІ) under solid-state condition. Purified CMCase-I was novel because it was apparently holoenzyme in nature. The enzyme was monomeric as its native and subunit mass were almost the same, i.e., 43 and 42 kDa, respectively. Ea for carboxymethylcellulose (CMC) hydrolysis was 36.2 kJ mol−1. The enzyme was stable over a pH range of 3.5–6.5, while temperature optimum was 55 °C. Vmax, Km and kcat for CMC hydrolysis were 39 U mg−1 protein, 6.25 mg CMC mL−1 and 27.5 s−1, respectively. The pKa1 and pKa2 of ionizable groups of active site were 2.8 and 7.4, respectively. Thermodynamic parameters for CMC hydrolysis were as follows: ΔH* = 33.5 kJ mol−1, ΔG* = 70.42 kJ mol−1 and ΔS* = −114.37 J mol−1 K−1. The removal of metals resulted into complete loss of enzymatic activity and was completely recovered in the presence of 1 mM Mn2+, whereas inhibition initiated at 5 mM. The other metals like Ca2+, Zn2+ and K1+ showed no inhibition up to 7 mM, Co2+ completely inhibited the activity, while Mg2+ could not recover the initial activity up to 7 mM. So we are reporting for the first time, kinetics and thermodynamics of CMCase-Ι from G. citrina.

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