Partial characterisation of human and porcine adipose acidic protease activity

1. An aspartic protease was isolated from human and porcine white adipose tissue and from isolated human adipocytes. The three preparations appeared to represent the same enzyme. 2. Electrofocusing of all three preparations revealed two bands corresponding to a pI of 3.6 and 4.4. respectively. On PAGE a single band in the same position was obtained in all three cases. 3. Both the porcine and human fractions were optimally active at pH 3.4, using acid denatured haemoglobin as substrate, and both activities were strongly inhibited by pepstatin and iodoacetate. 4. The Km values for haemoglobin for the porcine and human proteases were 0.16 and 0.14 mM respectively, whereas Vmax values of 30 and 33 units.nmol-1, respectively, were obtained.