Isocitrate lyase activity in the regenerating forelimb of the adult newt

✍ Scribed by Jasch, Laura G. ;Schmidt, Anthony J.

• Publisher: John Wiley and Sons
• Year: 1974
• Tongue: English
• Weight: 926 KB
• Volume: 190
• Category: Article
• ISSN: 0022-104X
• DOI: 10.1002/jez.1401900209

✦ Synopsis

Abstract

Regenerating and non‐regenerating limb tissues from the adult newt, Diemictylus viridescens, were assayed for isocitrate lyase activity. The enzyme assays were performed by micromodifications of existing procedures. In general, the whole homogenate, or a soluble fraction of the homogenate, was incubated with the substrate isocitrate. Isocitrate is cleaved by isocitrate lyase to glyoxylate and succinate. At the termination of the reaction, the 2,4‐dinitrophenylhydrazone derivative of glyoxylate was produced, extracted and quantitated spectrophotometrically. Isocitrate lyase activity was localized to bulb and two‐digit regenerates. The reaction product, glyoxylate (a monocarboxylic keto acid), was of special interest due to its role as a potent in vitro metabolic inhibitor. Therefore, the endogenous level of monocarboxylic keto acids, and the ability of regenerating tissue to produce and accumulate monocarboxylic keto acids, were investigated. Whole homogenates of regenerating tissue always contained more monocarboxylic keto acids than intact forearm or stump tissue. Also, after 30 minutes incubation with buffer alone, only regenerating tissue produced and accumulated additional monocarboxylic keto acids. In regenerating tissue, the isocitrate lyase reaction may be utilized in the metabolism of lipid. Since regenerating tissue can produce and accumulate monocarboxylic keto acids in vitro, glyoxylate produced by the isocitrate lyase reaction may accumulate in vivo and participate in metabolic regulation.