Midgut mitochondrial transhydrogenase in wandering stage larvae of the tobacco hornworm, Manduca sexta

Arch Insect Biochem Physiol. 2008 Nov;69(3):118-26. doi: 10.1002/arch.20277.

Abstract

Midgut mitochondria from fifth larval instar Manduca sexta exhibited a transhydrogenase that catalyzes the following reversible reaction: NADPH + NAD(+) <--> NADP(+) + NADH. The NADPH-forming transhydrogenation occurred as a nonenergy- and energy-linked activity. Energy for the latter was derived from the electron transport-dependent utilization of NADH or succinate, or from Mg++-dependent ATP hydrolysis by ATPase. The NADH-forming and all of the NADPH-forming reactions appeared optimal at pH 7.5, were stable to prolonged dialysis, and displayed thermal lability. N,N'-dicyclohexylcarbodiimide (DCCD) inhibited the NADPH --> NAD(+) and energy-linked NADH --> NADP(+) transhydrogenations, but not the nonenergy-linked NADH --> NADP(+) reaction. Oligomycin only inhibited the ATP-dependent energy-linked activity. The NADH-forming, nonenergy-linked NADPH-forming, and the energy-linked NADPH-forming activities were membrane-associated in M. sexta mitochondria. This is the first demonstration of the reversibility of the M. sexta mitochondrial transhydrogenase and, more importantly, the occurrence of nonenergy-linked and energy-linked NADH --> NADP(+) transhydrogenations. The potential relationship of the transhydrogenase to the mitochondrial, NADPH-utilizing ecdysone-20 monooxygenase of M. sexta is considered.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Animals
  • Dialysis
  • Dicyclohexylcarbodiimide / pharmacology
  • Gastrointestinal Tract / enzymology
  • Hot Temperature
  • Hydrogen-Ion Concentration
  • Larva / enzymology
  • Manduca / enzymology*
  • NADP Transhydrogenases / antagonists & inhibitors
  • NADP Transhydrogenases / metabolism*
  • Oligomycins / pharmacology

Substances

  • Oligomycins
  • Dicyclohexylcarbodiimide
  • NADP Transhydrogenases