The synthesis of taurocholic and glycocholic acids by preparations of human liver: II. An analysis of the stimulating effect of the L fraction

• Published in: Biochimica et biophysica acta. General subjects Vol. 141; no. 1; pp. 155 - 163
• Main Authors: Scherstén, Tore, Björntorp, Per, Ekdahl, Per-H, Björkerud, Sören
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 13.06.1967
• DOI: 10.1016/0304-4165(67)90254-1
• ISSN: 0304-4165

1. 1. A further analysis was made of the centrifugal lysosome fraction (L fraction) stimulation of microsomal synthesis of bile acid conjugates demonstrated in the previous paper. 2. 2. In subfraction of homogenate from human liver, the activity that stimulated synthesis of taurocholic and glycocholic acids was distributed in the same manner as acid phosphatase activity, while glucose-6-phosphatase (EC3.1.3.9) had a different distribution. 3. 3. The factor stimulating synthesis could be rendered soluble by freezing and thawing the L fraction. The supernatant after centrifugating frozen and thawed L fraction showed a specific conjugation-stimulating capacity that was 5 times as high as that untreated L fraction. The factor was rendered inactive by heating up to 100° for a short period, and could not be dialysed with any security. The supernatant, with a high capacity for stimulating microsomal synthesis of bile acid conjugate, had no capacity for synthesising chol-hydroxamic acid on incubation with hydroxylamine. 4. 4. With further centrifugating of the L fraction in a sucrose gradient, a light L fraction and a heavy L fraction were obtained, as described earlier. The light L fraction showed about 10 times as high acid phosphatase (EC 3.1.3.2) activity, and a capacity for stimulatinf conjugate synthesis about 8 times as great, as those found in the unpurified L fraction. The fraction did not form chol-hydroxamic acid on incubation with hydroxylamine. The heavy L fraction had no stimulatinf effect on the synthesis of bile acid conjugate, and no capacity for forming chol-hydroxamic acid. 5. 5. The results provide further evidence that the microsomes are carriers of the bile acid-activating enzyme and the lysosomes, or another component of the L fraction, for instance the peroxisomes, of the transferring enzyme or enzymes.