In Kreb's cycle and Urea cycle the linking component is

Urea cycle * Cleavage of argininosuccinate by argininosuccinate lyase, results in formation of arginine and release of the aspaate skeleton as fumarate (funnelled into TCA cycle) * Subsequent addition of water to fumarate forms l-malate, with subsequent oxidation forms oxaloacetate, followed by its transamination by glutamate aminotransferase then re-forms aspaate. * Argininosuccinate synthase links aspaate and citrulline forms argininosuccinate. * Thus the urea cycle is linked to TCA cycle through fumarate Ref:- Harper 30/e; pg num:- 294