Interrelation of delta-aminolevulinic acid and brain myelin proteins as affected by benzene and lead

An experimental model of subacute lead and benzene intoxication was induced in rabbits. It increased significantly delta-aminolevulinic acid (14C-ALA) incorporation into CNS myelin. ALA stably fixes on myelin proteins, especially Wolfgram proteins. In spite of this about one half of ALA incorporated into myelin linked with its basic proteins. Lead and benzene intoxication cause changes in the proportion of the basic fractions of myelin proteins. The amount of basic proteins increases, while the amount of proteolipid and Wolfgram proteins decreases. Lead and especially benzene intoxication decreases exogenous ALA insertion into basic proteins and proteolipid proteins, with ALA fixation on Wolfgram proteins remaining unchanged.     

Lectin-binding proteins in central-nervous-system myelin. Binding of glycoproteins in purified myelin to immobilized lectins

The capacities of immature and mature rat brain myelin, bovine myelin and human myelin to be agglutinated by soya-bean agglutinin, Ricinus communis agglutinin, wheatgerm agglutinin, and Lotus tetragonolobus agglutinin were examined. The first two lectins, which are specific for galactose and N-acetylgalactosamine, strongly agglutinated immature and mature rat myelin, weakly agglutinated bovine myelin, but did not affect human myelin. The other myelin and lectin combinations resulted in very weak or no agglutination. [(3)H]Fucose-labelled glycoproteins of purified adult rat brain myelin were solubilized with sodium dodecyl sulphate and allowed to bind to concanavalin A-Sepharose and each of the other lectins mentioned above, which had been immobilized on agarose. About 60% of the radioactive fucose was in glycoproteins that bound to concanavalin A-Sepharose and these glycoproteins could be eluted with solutions containing methyl alpha-d-mannoside and sodium dodecyl sulphate. Periodate/Schiff staining or radioactive counting of analytical gels showed that most of the major myelin-associated glycoprotein (apparent mol.wt. approx. 100000) bound to the concanavalin A, whereas the glycoproteins that did not bind were mostly of lower molecular weight. Preparative polyacrylamide-gel electrophoresis of the glycoprotein fraction that was eluted with methyl alpha-d-mannoside yielded a relatively pure preparation of the myelin-associated glycoprotein. Similar results were obtained with each of the other lectins, i.e. the myelin-associated glycoprotein was in the fraction that bound to the immobilized lectin. Double-labelling experiments utilizing [(3)H]fucose-labelled glycoproteins from adult myelin and [(14)C]fucose-labelled glycoproteins from 14-day-old rat brain myelin did not reveal any difference in the binding of the mature and immature glycoproteins to any of the immobilized lectins. The results in this and the preceding paper [McIntyre, Quarles & Brady (1979) Biochem. J.183, 205-212] suggest that the myelin-associated glycoprotein is one of the principal receptors for concanavalin A and other lectins in myelin, and that this property can be utilized for the purification of this glycoprotein.     

Binding of all-trans-retinoic acid to MLTC-1 proteins

The covalent incorporation of [³H]all-trans-retinoic acid into proteins has been studied in tumoural Leydig (MLTC-1) cells. The maximum retinoylation activity of MLTC-1 cell proteins was 710 ± 29 mean ± SD) fmoles/8 × 10⁴ cells at 37 °C. About 90% of [³H]retinoic acid was trichloroacetic acid-soluble after proteinase-K digestion and about 65–75% after hydrolysis with hydroxylamine. Thus, retinoic acid is most probably linked to proteins as a thiol ester. The retinoylation reaction was inhibited by 13-cis-retinoic acid and 9-cis-retinoic acid with IC₅₀ values of 0.9 μM and 0.65 μM, respectively. Retinoylation was not inhibited by high concentrations of palmitic or myristic acids (250 μM); but there was an increase of the binding activity of about 25% and 130%, respectively. On the other hand, the retinoylation reaction was inhibited (about 40%) by 250 μM lauric acid. After pre-incubation of the cells with different concentrations of unlabeled RA, the retinoylation reaction with 100 nM [³H]RA involved first an increase at 100 nM RA and then a decrease of retinoylation activity between 200 and 600 nM RA. After cycloheximide treatment of the tumoural Leydig cells the binding activity of [³H]RA was about the same as that in the control, suggesting that the bond occurred on proteins in pre-existing cells. (Mol Cell Biochem 276: 55–60, 2005)This paper is dedicated to the memory of Prof. E. Quagliariello.     

Biosynthesis of delta-aminolevulinic acid by blue-green algae (cyanobacteria).

When levulinic acid, a competitive inhibitor of delta-aminolevulinic acid dehydratase, was added to growing cultures of blue-green algae (cyanobacteria), delta-aminolevulinic acid was excreted into the medium and cell growth was inhibited.     

Inherited deficiency of delta-aminolevulinic acid dehydratase.

Delta-aminolevulinic acid dehydratase (ALA-D) is the second enzyme in the porphyrin-heme pathway and converts delta-aminolevulinc acid (ALA) to porphobilinogen (PBG). A family is reported with an inherited deficiency of red cell ALA-D activity occurring over three generations in an autosomal dominant pattern. Intial experiments support the hypothesis that the mutation in this family may affect a regulatory gene, but enzyme purification and further study are required. Although no clinical manifestations of deficient ALA-D activity have been found in affected persons, families such as this may be at increased risk for the serious consequences of lead poisoning, which produces marked inhibition of ALA-D activity.     

Binding of extracellular matrix proteins by lactobacilli

Ten gut and ten vaginalLactobacillus strains were investigated for their ability to bind type I collagen (Cn-I) and four selected gut lactobacilli were investigated for their binding to other extracellular matrix (ECM) molecules. Immobilized Cn-I (100 mg/L) in wells of microtitre plates was bound by all 10 autoaggregating vaginal strains and by 3 strains of gut lactobacilli from piglets in the range ofA ₅₇₀ readings 0.114–1.806.L. acidophilus strain SV31 was much more adherent than the rest of strains. All four gut lactobacilli tested for binding to other ECM molecules displayed good binding to porcine fibronectin and heparin and some of them bound weakly to fetuin and porcine mucin. No binding of these strains was observed to bovine mucin, bovine fibrinogen and bovine lactoferrin.     

Automated assay for delta-aminolevulinic acid dehydratase.

An automated procedure for the assay of semipurified and purified δ-aminolevulinic acid dehydratase (EC 4.2.1.24) has been developed based on the manual spectrophotometric method of Mauzerall and Granick (1). This method has been used to determine (a) the enzyme activity in various samples during enzyme-purification procedures, (b) the dependence of initial rates of catalysis for a fixed enzyme concentration on the substrate concentration, and (c) the variation in the level of enzyme activity during and after chemical modification.     

Studies on adrenal delta-aminolevulinic acid synthetase.

The presence of δ-aminolevulinic acid synthetase (EC 2.3.1.37) in rat and bovine adrenals has been demonstrated. When untreated animals are employed, the activity of δ-aminolevulinic acid synthetase in rat and bovine adrenal homogenates is comparable to the activity found in hepatic homogenates. Adrenal δ-aminolevulinic acid synthetase is localized in the mitochondrial fraction and appears to be refractory to induction by agents that induce the hepatic enzyme. Starvation of rats increased adrenal δ-aminolevulinic acid synthetase activity without altering the activity of the hepatic enzyme. Treatment of rats with adrenocorticotropin also dramatically increased adrenal δ-aminolevulinic acid synthetase activity. These results suggest that the adrenal enzyme may be controlled by factors that differ from those which regulate the activity of the hepatic enzyme.     

Effect of delta-aminolevulinic acid on frog nerve-muscle function

Effects of delta-aminolevulinic acid (ALA) on nerve-muscle function $\text{in vitro}$ have been examined using the frog sciatic gastrocnemius preparation. Levels of ALA that did not interfere with nerve conduction did inhibit the muscle's response to nerve stimulation for a period of 50 – 120 min. The amounts of ALA within muscle were declining at 2 hr after topical administration. It is suggested that some of the symptoms in acute attacks of intermittent porphyria may be attributable to effects from ALA.     

Distribution of delta-aminolevulinic acid synthetase and delta-aminolevulinic acid dehydratase in liver and kidney of rainbow trout (Salmo gairdnerii)

1. Activities of delta-aminolevulinic acid synthetase (ALA-S) and delta-aminolevulinic acid dehydratase (ALA-D) in trout liver and kidney were compared with those in the mouse. 2. ALA-S activity (per unit tissue fresh weight) exceeded ALA-D activity in trout liver and kidney. 3. In trout kidney, ALA-S activity slightly exceeded, and ALA-D activity far exceeded, their activities in trout liver. 4. In trout, heme synthesis differs from that in mammals in that appreciable synthesis occurs in the kidney, and in that ALA-S activity is not rate limiting.