English: Amino acid catabolism. This is a modified version of a diagram created July 2011 by Mikael Häggström and based on information in Lippincott's Illustrated Reviews: Biochemistry^[1]. The Lippincott's text and the original diagram contained several discrepancies when compared with 5 other prominent biochemistry textbooks.

This revised diagram represents consensus information from these 5 texts (see References below).

Specific updates:

-There is a lack of agreement among textbooks about which amino acids enter at acetoacetate, which enter at acetoacetyl CoA, and which enter directly at acetyl CoA. However, the key point is that there are 7 amino acids that enter the TCA at acetyl CoA, and the diagram has been revised to reflect this.

-Threonine was previously listed as glucogenic only, but it is both glucogenic and ketogenic (enters at acetyl CoA) and has been updated accordingly.

-Tryptophan was listed as both glucogenic and ketogenic, yet the old version of the diagram did not have it entering at any glucogenic substrate. Diagram has been updated to show it enters at pyruvate.

-Only Phenylalanine and Tyrosine were listed as entering at Fumarate, but Aspartate also does. The diagram has been updated accordingly.

References:

Garrett, R. H., & Grisham, C. M. (2008). Biochemistry (5 ed.): Brooks Cole. See p. 805.

Gropper, S. S., Smith, J. L., & Groff, J. L. (2009). Advanced Nutrition and Human Metabolism (5 ed.). Belmont, CA: Wadsworth Publishing Company, Inc. See p. 212.

Murray, R. K., Bender, D., Rodwell, V. W., Botham, K. M., Kennelly, P. J., & Weil, P. A. (2009). Harper's Illustrated Biochemistry (28 ed.): McGraw-Hill Medical. See p. 505.

Nelson, D. L., & Cox, M. M. (2009). Lehninger Principles of Biochemistry (5 ed.): W.H. Freeman and Company. See p. 688.

Stipanuk, M. H. (2006). Biochemical, physiological, & molecular aspects of human nutrition (2 ed.): Saunders Elsevier. See p. 369.