Considering the evidence that led Krebs to propose a cyclic pathway for oxidation of pyruvate, discuss the type of experimental evidence that might have led to realization of the cyclic nature of the glyoxylate pathway. 1-2 pages APA with references and in text citations |
 

Glyoxylate Cycle

            Many plants and other small living organisms like bacteria can support themselves on acetate and other compounds that produce Coenzyme A (CoA). These plants, in most cases, utilize the metabolic pathway that lacks in many organisms that primarily converts two-carbon acetyl units to four-carbon units that are primarily used in energy production and biosynthesis; this is a reaction sequence that is known as the Glyoxylate cycle; This cycle eliminates the citric acid cycle's two de-carboxylation procedures. Another important distinction is that molecules of acetyl CoA join the Glyoxylate cycle in turn, whereas only one enters the citric acid cycle.

            The Glyoxylate cycle is similar to the citric acid cycle, however, with a little modification. While continuing his research on plant respiration, Hans Krebs tasked Harry Beevers and Hans Kornberg with finding a mechanism involved in the conversion of fat to carbs, primarily in plants (BEEVERS, 1980). Beevers and Kornberg discovered malate synthase and isocitrate lyase in the endosperm of castor beans while working together; this discovery prompted Beevers and Kornberg to begin their research towards defining and comprehending the Glyoxylate cycle (BEEVERS, 1980).

            Beevers and Kornberg discovered that succinate, which is primarily formed from acetate, functioned as a precursor for glucose by reversing glycolysis in their effort to prove that the Glyoxylate cycle was converting fat to sugar in plants (BEEVERS, 1980). This experiment also demonstrated that the tricarboxylic acid cycle was rarely active during plant germination but that acetate was promptly converted into sugar by the glyoxalate shunt. During growth, plants require a significant amount of carbohydrates for wall production; thus, in the absence of carbs, the glyoxalate shunt offers sugar derived from acetyl CoA produced by fatty acid oxidation. The Glyoxylate cycle occurs in glyoxysomes, which are organelles found in plants (BEEVERS, 1980).