Improved method for measurement of delta-aminolevulinic acid dehydratase activity of human erythrocytes.
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In a study of the urinary excretion of haem precursors in patients with rheumatoid arthritis, iron-deficiency anaemia, and in healthy controls, certain differences were found. In iron-deficiency anaemia the excretion of both porphobilinogen and delta-aminolevulinic acid was increased, whereas in patients with rheumatoid arthritis only the porphobilinogen excretion was increased.A further study on the erythrocyte activity of delta-aminolevulinic acid dehydrase showed a higher activity in the erythrocytes from patients with rheumatoid arthritis compared with healthy controls.
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The distribution of phospholipids from labeled parental membranes to progeny cells was studied by autoradiography and a minicell system. The minicell experiments showed that, during growth, the parental membrane is diluted at the same rate in cells and in minicells, which indicates that ends of cells are not different from the cylindrical portions with regard to the distribution of parental molecules. The same result was obtained after labeling heme-containing proteins with delta-aminolevulinic acid. The autoradiographic experiments indicate that the membrane segregates in about 250 subunits 4 x 10(4) nm(2) in size. These subunits appear to be conserved during growth.
Three micromethods are described for the assay of enzymes or products of the heme biosynthetic pathway in blood. A fluorometric method for the assay of protoporphyrin may be applied to the rapid screening of children for chronic lead poisoning. A colorimetric assay for delta-aminolevulinic-acid dehydratase may be applied to the detection of acute and chronic lead poisoning. A fluorometric assay for porphyrin formation from prophobilinogen is also described.
The substrate binding site of aspartate-beta-semialdehyde dehydrogenase from Escherichia coli was studied by affinity labeling with L-2-amino-4-oxo-5-chloropentanoic acid. The substrate analogue irreversibly inactivates the enzyme with pseudo-first-order kinetics and with a half-of-the-sites reactivity. The substrate aspartate beta-semialdehyde protects the enzyme against the inactivation. A single group is labeled at the active site and is concluded to be the side-chain of a histidine residue. The amino acid sequence around the active site residue was established from a peptic digest of the labeled enzyme: Phe-Val-Gly-Gly-Asp-(modified residue)-Thr-Val-Ser.
Glucagon elicits a twofold increase in delta-aminolevulinic acid synthetase activity in the livers of 18-day-old chick embryos. This rise occurs when RNA synthesis is inhibited, but is prevented when protein synthesis is blocked. Cyclic adenosine monophosphate appears not to be involved.
The origin of the methyl group on C-1 of Ring A of the corrin ring of vitamin B(12) was investigated by (13)C magnetic resonance spectroscopy. The proton-decoupled (13)C spectra of vitamin B(12) synthesized from [5-(13)C]delta-aminolevulinic acid by Propionibacteria were obtained by Fourier-transform nuclear magnetic resonance of high resolution, and spectra of high-resolution proton magnetic resonance of the (13)C-labeled B(12) were also taken. The delta-carbon atom of delta-aminolevulinic acid is the source of seven or eight known positions of vitamin B(12), depending on whether the C-1 methyl group is also derived from the labeled substrate. We have found seven resonances whose chemical shifts enable us to identify the position of the (13)C atoms in the molecule from the assignment of Dodderell and Allerhand. We observed no (13)C resonance corresponding to the C-1 methyl group of Ring A. Furthermore, the proton magnetic resonance spectrum showed no spin-spin splitting of the proton peak at the tau values assigned for the H atoms in this methyl group. It would thus appear that the methyl group at C-1, which has been considered to have the same origin as the delta-methine bridge of porphyrins, does not originate from the delta-carbon atom of delta-aminolevulinic acid. This finding may aid in elucidation of the mechanism of synthesis of the functional isomer of vitamin B(12) and porphyrins. The (13)C-labeled vitamin B(12) enabled us to make further assignments to the (13)C magnetic resonance of the vitamin.
The effects of urinary volume on daily urinary excretion of seven heavy metals and four organic substances were examined in relation to the changes in their plasma and erythrocyte concentrations and urinary creatinine excretion in 19 metal workers. The examination was conducted under the conditions of water restriction and loading for six days. The major findings were as follows: (1) urinary excretion of all heavy metals and organic substances except mercury, together with creatinine excretion, significantly decreased under the water restrictive condition whereas under the water loading condition their excretion significantly increased and (2) daily variations in urinary excretion of lead, cadmium, chromium, copper, hippuric acid, delta-aminolaevulinic acid, and coproporphyrin did not differ significantly from the variation in urinary excretion of creatinine (profile analysis, p greater than 0.05). It is suggested that glomerular filtration is the major factor determining renal excretory mechanisms of the four heavy metals and three organic substances examined.