The absence of glyoxylate cycle enzymes in rodent and embryonic chick liver.

There have been several reports over the past decade of the presence of the glyoxylate cycle enzymes, isocitrate lyase and malate synthase, in animal tissues. Reaction products in these assays have been measured principally by chromatographic separation of isotopes or by colorimetric procedures. In this report more sensitive and accurate HPLC and HPCE analyses were used to detect enzymatic activity. Reversed phase HPLC revealed the absence of detectable isocitrate lyase activity in guinea pig, rat and chick embryonic liver. The formation of several other alpha-keto acids was detected and this may account for the previously reported activities. Using HPCE to monitor malate formation malate synthase activity was not detected in these tissues. These results indicate that when assaying enzyme activities in crude tissue homogenates specific methods for the identification of end products are required.