Physicochemical and Kinetic Characteristics of Isoforms of Isocitrate Lyase from Corn

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A. T. Eprintsev, E. V. Maslova, D. N. Fedorin, and V. N. Popov^*

Voronezh State University, Universitetskaya pl. 1, 394006 Voronezh, Russia; fax: (473) 220-8755; E-mail: bc366@bio.vsu.ru

^* To whom correspondence should be addressed.

Received January 28, 2008; Revision received March 19, 2008

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Three electrophoretically homogeneous isocitrate lyase (ICL) isoforms were obtained by 4-step purification from corn scutellum (ICL₁ and ICL₂) and green leaves (ICL). Their physicochemical, kinetic, and regulatory properties were analyzed. The molecular masses of ICL₁, ICL₂ , and ICL isoforms determined by gel filtration are 164, 207, and 208 kDa, respectively. The proteins have homotetrameric quaternary structure with subunit molecular masses of 43, 48, and 47 kDa for ICL₁, ICL₂, and ICL, respectively. We found some differences in pH optimum, K_m, and regulation by divalent metal cations between ICL₁ and ICL₂ and significant similarity of ICL₂ and ICL. Based on these data, we suggest the participation of these isoforms in metabolic regulation of the glyoxylate cycle, organic acid metabolism during photorespiration in leaves and acidosis in corn seeds.

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KEY WORDS: isocitrate lyase, isoforms, electrophoresis, quaternary structure, subunits, glyoxylate cycle, gluconeogenesis

DOI: 10.1134/S0006297909050071

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