Effect of long-term cyanide exposure on cyanide-sensitive respiration and phosphate metabolism in the fungus Phycomyces blakesleeanus

Marina Stanic,M Zivic,S Krizak,Joanna Zakrzewska,Aleksandra Pajdic,Mirzeta Hadzibrahimovic,M Zizic

doi:10.2298/abs1402847s

Abstract

The effects of long-term exposure (5 h) of Phycomyces blakesleeanus mycelium to 5 mM KCN on respiration and phosphate metabolites were tested. Exposure to cyanide, antimycin A and azide lead to a decrease in the activity of cyanide-sensitive respiration (CSR), and the ratio of core polyphosphates (PPc) and inorganic phosphates (Pi), which is a good indicator of the metabolic state of a cell. After 5 h of incubation, the activity of CSR returned to control values. For this, the recovery of cytochrome c oxidase (COX) was required. In addition, the PPc/Pi ratio started to recover shortly after initiation of COX recovery, but never reached control values. This led us to conclude that the regulation of polyphosphate (PPn) levels in the cell is tightly coupled to respiratory chain functioning. In addition, acutely applied cyanide caused two different responses, observed by 31P NMR spectroscopy, that were probably mediated through the mechanism of glycolytic oscillations, triggered by the effect of cyanide on mitochondria.

Highlights

It is generally thought that polyphosphates (PPn) play an important role in fungal energy metabolism since they regulate the level of ATP and function as either a high-energy reserve or a phosphate reserve via hydrolysis (Harold, 1966; Kulaev and Kulakovskaya, 2000)
It was shown previously that incubation in antimycin A increases the activity of cyanide-resistant respiration (Živić et al, 2009); here we compared the effects of long-term exposure of P. blakesleeanus mycelium to cyanide (5 mM) and antimycin A (20 μM)
When the P. blakesleeanus mycelium was incubated in antimycin A, there were no changes in Cyanide-resistant respiration (CRR) participation during incubation and no cyanide-sensitive respiration (CSR) recovery (Fig. 1A and B, black circles)

Summary

INTRODUCTION

It is generally thought that polyphosphates (PPn) play an important role in fungal energy metabolism since they regulate the level of ATP and function as either a high-energy reserve or a phosphate reserve via hydrolysis (Harold, 1966; Kulaev and Kulakovskaya, 2000). Our previous research (Zakrzewska et al, 2005) has shown that cyanide, a common blocker of cytochrome c oxidase (COX), unlike azide, increases this parameter. Was not performed with cyanide, whose target is cytochrome c oxidase (COX), instead of Complex III It was shown by Schubert and Brill (1968) that there can be a recovery of COX function after cyanide application. Our previous work (Zakrzewska et al, 2005) has shown that cyanide may express some specific effects compared to other conventional inhibitors of cytochrome respiratory chain, like azide and antimycin A. In order to accomplish this, we have simultaneously measured the effects of three common respiratory inhibitors, cyanide, antimycin A and azide, on 31P NMR spectra and respiration of P. blakesleeanus during prolonged periods of incubation

MATERIALS AND METHODS

RESULTS

DISCUSSION