The number of time(s) decarboxylation of isocitrate occurs during single TCA cycle is 

The number of times decarboxylation of isocitrate occurs during a single TCA cycle is two. 

During the TCA cycle, the decarboxylation of isocitrate occurs in two distinct steps:Isocitrate is fi rst converted to $\alpha$-ketoglutarate through a decarboxylation reaction, where one molecule of CO₂ is released.  Isocitrate $\to \alpha$-ketoglutarate + CO₂ . The $\alpha$-ketoglutarate formed in the previous step is then decarboxylated again to succinyl CoA, resulting in the release of a second molecule of CO₂. $\alpha$-ketoglutarate$\to$ Succinyl-CoA + CO₂