Human Hepatic δ-Aminolaevulinate Synthase: Requirement of an Exogenous System for Succinyl-Coenzyme a Generation to Demonstrate Increased Activity in Cirrhotic and Anticonvulsant-Treated Subjects

Abstract

1. We have studied activity of delta-aminolaevulinate synthase in needle liver biopsy specimens obtained from 12 human cirrhotic subjects, five subjects who had ingested anticonvulsants and from control subjects. Liver iron concentrations and quantitative urinary excretions of porphyrins plus their precursors were also determined. 2. In liver homogenates from subjects of each group, addition of an exogenous system for generation of succinyl-coenzyme A (CoA), including succinic thiokinase, resulted in appreciable enhancement of activity beyond that obtained without this system. 3. Mean activities for delta-aminolaevulinate synthease were not significantly different among patient groups when assayed without the exogenous succinyl-CoA-generating system, but liver homogenates from cirrhotic patients and subjects ingesting anticonvulsants had significantly higher activities than control subjects in the presence of the succinyl-CoA-generating system. 4. Although mean liver iron concentration in the cirrhotic group was slightly higher than in control subjects, and in control subjects there was some correlation between liver iron concentration and activity of delta-aminolaevulinate synthase, variations in this activity could not be accounted for solely on the basis of chronic hepatic deposition. Nor were these variations ascribable to differences among subjects in ingestion of ethanol before biopsy or severity of hepatic inflammation as judged biochemically and histologically. 5. Cirrhotic subjects excreted more uro- and copro-porphyrin than control subjects, whereas subjects ingesting anticonvulsants excreted more delta-aminolaevulinic acid and porphobilinogen than control subjects. However, these increases were small and not sufficient to account for all the increased delta-aminolaevulinic acid which potentially could have been formed by these subjects. 6. These considerations raise the possibilities that in vivo: (a) rate of human hepatic synthesis of delta-aminolaevulinic acid is modulated by the supply of succinyl-CoA; (b) the rate of hepatic synthesis of haem is increased in cirrhotic patients and subjects ingesting anticonvulsants; (c) other important routes exist for disposition of haem precursors in these subjects, besides utilization for haem synthesis.

The role of haem biosynthetic and degradative enzymes in erythroid colony development: the effect of haemin

“…ALAS activity was measured by a radiochemical method utilizing 14C-succinate in the presence of a succinyl-CoA generating system. This system has been reported to be required for the assay of ALAS by other investigators utilizing other tissues for the enzyme assay (Wolfson et al, 1980;Bonkowsky & Pomeroy, 1977). The ALAS microassay system reported here has also been shown to be applicable to measurement of this enzyme activity in the human erythroid leukaemic cell line K-562 (Hoffman et al, 1980).…”

“…After incubation, the cultures were harvested, washed as described above and spun down at 1000 g for 15 min. Cellular radioactive haem was extracted by the method of Bonkowsky et al (1978), after washing the cells four times with acetone. The haem was crystallized and washed with cold water.…”

Induction of delta‐aminolaevulinic acid synthase in leucocytes of patients on phenytoin therapy‐comparison with changes in rat hepatic tissue.

“…A number of drugs have been found to result in increased activity of ALA synthase in animal hepatic tissue and chick embryo culture preparations (Granick & Sassa, 1971). Increased activity of ALA synthase has been found in hepatic biopsy tissue of patients on phenytoin (DPH) or phenobarbitone anticonvulsant therapy (Bonkowsky & Pomeroy, 1977). A high proportion of the drugs which result in increased activity of ALA synthase also induce the mixed function oxidase (MFO) enzyme system with associated increase in cytochrome P-450 (Rifkind, Gillette, Song & Kappas, 1973).…”

Abnormal haem biosynthesis in chronic alcoholics

“…Increased hepatic ALA synthase activity also occurs in rats during chronic ethanol dosing [5]. Increased activity of hepatic ALA synthase has been reported in chronic alcoholic subjects with liver disease [6].…”