<prompt> All the following are false regarding C. diphteriae toxin EXCEPT:It is an endotoxinToxin production depends on optimum concentration of ironIt acts by activating adenyl cyclaseSchick Test demonstrates circulating toxin  <response>: Toxin production depends on optimum concentration of iron REF: Jawetz, Melnick, Adelbergs Medical Microbiology, 24TH edition Chapter 13. DIPHTHERIA TOXIN: Exotoxin Heat-labile polypeptide MW 62,000 Lethal in a dose of 0.1 ugkg Two fragments: Fragment B MW 38,000 has no independent activity but is required for the transpo of fragment A into the cell. Fragment A inhibits polypeptide chain elongation. provided nicotinamide adenine dinucleotide NAD is present--by inactivating the elongation factor EF-2. In vitro production of this toxin depends largely on the concentration of iron. Toxin production is optimal at 0.14 lig of iron per milliliter of medium but is viually suppressed at 0.5 ligmL. Other factors influencing the yield of toxin in vitro are osmotic pressure, amino acid concentration, pH, and availability of suitable carbon and nitrogen sources. The factors that control toxin production in vivo are not well understood. 