Figure 2.

Subcellular distribution of 2-HPCL activity in rat liver. A fresh rat liver homogenate was fractionated by differential centrifugation into a nuclear (N), a heavy mitochondrial (M), a light mitochondrial (L), a microsomal (P), and a cytosolic (S) fraction. The fractions were incubated with 2-hydroxy-3-methyl-[1-¹⁴C]hexadecanoyl-CoA, and labeled formate was measured as reaction product. In these experiments, no TPP or Mg²⁺ was present in the assay mixtures. Marker enzymes and protein were determined in each fraction: catalase (peroxisomal matrix), glutamate dehydrogenase (GDH, mitochondria), glucose-6-phosphatase (G-6-Pase, endoplasmic reticulum), acid phosphatase (Acid Pase, lysosomes), and lactate dehydrogenase (LDH, cytosol). Relative specific activities are presented vs. cumulative percentage of total protein (relative specific activity is defined as the percentage of total recovered activity in a given fraction vs. the percentage of total recovered protein in that fraction). Overall recovery for lyase was 92%; overall recoveries for marker enzymes were between 99 and 113%. Total lyase activity was 112.8 mU (nmol/min) per gram of liver. A similar distribution pattern was found in the presence of TPP and Mg²⁺ (V.F., K.C., G.P.M., P.P.V.V. and M.C., unpublished data).