Purification and characterization of DOPA-decarboxylase from adult gravid Aedes aegypti

Role of tyrosine, DOPA and decarboxylase enzymes in the synthesis of monoamines in the brain of the locust

The metabolic transformation of tyrosine (TYR) by the decarboxylase and hydroxylase enzymes was investigated in the central nervous system of the locust, Locusta migratoria. It has been demonstrated that the key amino acids, 3,4-dihydroxyphenylalanine (DOPA), 5-hydroxytryptophan (5HTP) and tyrosine are decarboxylated in all part of central nervous system. DOPA and 5HTP decarboxylase activities show parallel changes in the different ganglia, but the rank order of the activity of TYR decarboxylase is different. Enzyme purification has revealed that the molecular weights of TYR decarboxylase and DOPA/5HTP decarboxylase are 370,000 and 112,000, respectively. The decarboxylation of DOPA by DOPA/5HTP decarboxylase is stimulated, whereas the decarboxylation of DOPA by TYR decarboxylase is inhibited in the presence of the cofactor pyridoxal-5'-phosphate. TYR hydroxylase could not be detected and 3H-TYR is found to be metabolised to tyramine (TA), but not to DOPA. The haemolymph contains a significant concentration of DOPA (120 pmol/100 microl haemolymph), and the ganglia incorporates DOPA from the haemolymph by a high affinity uptake process (K(M)=12 microM and V(max)=24 pmol per ganglion/10 min). Our results suggest that no tyrosine hydroxylase is present in the locust CNS and the DOPA uptake into the ganglia by a high affinity uptake process as well as the DOPA decarboxylase enzyme may be responsible for the regulation of the ganglionic dopamine (DA) level. Two types of decarboxylases exist, one of them decarboxylating DOPA and 5HTP (DOPA/5HTP decarboxylase), other decarboxylating TYR (TYR decarboxylase). The DOPA/5HTP decarboxylase enzyme present in the insect brain may correspond to the 5HTP/DOPA decarboxylase in vertebrate brain, whereas TYR decarboxylase is characteristic only for the insect brain.

Sex determination and female reproductive development in the genus Schistosoma: a review

Parasites of the genus Schistosoma were among the first metazoans to develop separate sexes, which is chromosomally determined in the fertilized egg. Despite the occurrence of specific sex chromosomes, the females of most Schistosomatidae species do not complete their somatic development and reach no sexual maturity without the presence of males. Indeed, the most controversial and at the same time most fascinating aspect about the sexual development of Schistosoma females lies on discover the nature of the stimulus produced by males that triggers and controls this process. Although the nature of the stimulus (physical or chemical) is a source of controversy, there is agreement that mating is a necessary requirement for maturation to occur and for migration of the female to a definitive final site of residence in the vascular system of the vertebrate host. It has also been proposed that the stimulus is not species-specific and, in some cases, not even genus-specific. Despite a vast literature on the subject, the process or processes underlying the meeting of males and females in the circulatory system have not been determined and as yet no consensus exists about the nature of the stimulus that triggers and maintains female development. In the studies about their role, Schistosoma males have been considered, at times pejoratively, the brother, the muscles or even the liver of females. Indeed, it still remains to be determined whether the stimulus responsible for female maturation involves the transfer of hormones, nutrients, neuromediators, mere tactile stimulation or a combination of chemotactic and thigmotactic factors.

Purification and characterisation of L-DOPA decarboxylase from pharate pupae of Ceratitis capitata. A comparison with the enzyme purified from the white prepupae

In this paper we describe the purification of L-DOPA decarboxylase (DDC) to homogeneity from the developmental stage just before the eclosion (pharate pupae) of Ceratitis capitata. The enzyme was found to have a mol wt of approximately 100,000 and to be composed of two identical subunits (50,000 mol wt each). Polyclonal antibodies raised against the isolated enzyme reacted with the 50,000 dalton subunit and precipitated enzyme activity. Furthermore, properties of the enzyme isolated from the pharate pupa stage, were compared with those of DDC purified from the white prepupa stage with respect to substrate specificity, response to polyclonal antibodies, behaviour towards different cations and dependence of enzyme activity on the concentration of pyridoxal phosphate.

Purification and characterization of L-dopa decarboxylase from human kidney

L-dopa decarboxylase has been purified to homogeneity from post mortem removed human kidneys. Homogeneity was examined by polyacrylamide gel electrophoresis (PAGE) analysis both in the presence and absence of SDS. The enzyme has a molecular weight of 100,000 daltons estimated by gel filtration and 50,000 daltons determined after SDS-PAGE. Human L-dopa decarboxylase therefore is a dimer. Polyclonal antibodies produced against human L-dopa decarboxylase react with the 50,000 daltons enzyme subunit after immuno-blotting and also precipitates enzyme activity. Activity against L-dopa is partially inhibited by 5-hydroxytryptophan (5-HTP). The effect of various cations on L-dopa decarboxylase activity has also been tested.

L-dopa decarboxylase in Ceratitis capitata white puparia and human: a comparative study

1. L-DOPA decarboxylase (DDC) from Ceratitis capitata and from human kidney have been purified by the same methodology. 2. Both enzymes show mol. wts of 100,000, consisting of two identical mol. wt subunits and solely decarboxylate L-DOPA. 3. In the presence of 5-hydroxytryptophan (5-HTP) only the DDC activity from human kidney is remarkably reduced. 4. Addition of exogenous coenzyme is essential only for human DDC activity. 5. Polyclonal antibodies, raised against DDC purified from insects or humans, cross-react with both antigens.

Some aspects on L-dopa decarboxylase and p-tyrosine decarboxylase in the central nervous and peripheral tissues of the American cockroach Periplaneta americana

1. Aromatic amino acid decarboxylase activities toward L-DOPA (L-3,4-dihydroxyphenylalanine), 5-HTP (5-hydroxytryptophan) and p-tyrosine in different tissues of the sclerotized and newly ecdysed cockroach were analyzed. 2. The ratios of enzyme activity with regard to L-DOPA and p-tyrosine varied considerably in the tissues and between the two different growth stages. 3. A DOPA decarboxylase and a p-tyrosine decarboxylase were separated by gel filtration and ion exchange chromatography. 4. The optimal pH requirement for both enzymes was 7.5 with the exception of the one decarboxylating 5-HTP. 5. The molecular weights of the cockroach brain DOPA decarboxylase and tyrosine decarboxylase were estimated to be 120,000 and 100,000, respectively. 6. Unlike the mammalian aromatic amino acid decarboxylase, the cockroach DOPA decarboxylase cannot be activated by a small amount of benzene. 7. An increase of over 50-fold of DOPA decarboxylase activity and a 50% reduction of tyrosine decarboxylase activity in the epidermal tissue of the newly ecdysed animals was observed. 8. In the fully sclerotized cockroach, a reversible endogenous inhibitor(s) of DOPA decarboxylase in the integument was observed, suggesting that the DOPA decarboxylase is suppressed in the epidermal tissues when ecdysis does not occur.