Human porphobilinogen deaminase sequences

Details Human porphobilinogen deaminase sequences Human porphobilinogen deaminase sequences

1999-07-22

2003-03-25

Crouch, Deborah (Department: 1632)

Chemistry: molecular biology and microbiology

Micro-organism, tissue cell culture or enzyme using process...

Recombinant dna technique included in method of making a...

C435S070100, C435S071100, C435S252300, C536S023100, C536S023500

Reexamination Certificate

active

06537777

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to novel methods of treating and preventing disease caused by absence or deficiency of the activity of enzymes belonging to the heme biosynthetic pathway. More specifically, the invention pertains to methods of alleviating the symptoms of certain porphyrias, notably acute intermittent porphyria including gene therapy, therapy with a combination of encymatically active substances and therapy with recombinant produced enzymes such as PBGD. In addition the invention relates to an expression plasmid and a linear DNA fragment for use in the production of rhPBGD.
BACKGROUND OF THE INVENTION
Heme Biosynthetic Pathway
Heme is a vital molecule for life in all living higher animal species. Heme is involved in such important processes as oxygen transportation (haemoglobin), drug detoxification (cytochrome P450), and electron transfer for the generation of chemical energy (ATP) during oxidative phosphorylation in mitochondria.
Heme is synthesised in eight consecutive enzymatic steps starting with glycin and succinyl-CoA. Sassa S. 1996, Blood Review, 10, 53-58 shows a schematic drawing (
FIG. 1
in the article) of the heme biosynthetic pathway indicating that the first enzymatic step (delta-aminolevulinic-synthetase) and the last three steps (coproporphyrinogen oxidase, protoprophyrinogen oxidase and ferrochelatase) are located in the mitochondrion whereas, the remaining are cytosolic enzymes.
Important regulation of the heme biosynthetic pathway is delivered by the end product of the metabolic pathway, namely heme, which exerts a negative inhibition on the first rate-limiting enzymatic step (conducted by delta-aminolevulinic-synthetase) in the heme biosynthetic pathway (Strand et al. 1970, Proc. Natl. Acad. Sci. 67, 1315-1320).
Deficiencies in the heme biosynthetic enzymes have been reported leading to a group of diseases collectively called porphyrias.
A defect in the third enzymatic step leads to acute intermittent porphyria, AIP.
Acute Intermittent Porphyria
Acute intermittent porphyria (AIP) is an autosomal dominant disorder in man caused by a defect (50% reduction of activity) of the third enzyme in the heme biosynthetic pathway, prophobilinogen deaminase, (also known as porphobilinogen ammonia-lyase (polymerizing)), E.C. 4.3.1.8. (Waldenström 1937, J. Acta.Med. Scand. Suppl.82). In the following, this enzyme and the recombinant human form will be termed “PBGD” and “rhPBGD”, respectively.
Clinical Manifestation of AIP
The reduction is enzymatic PBGD activity makes this enzyme the rate limiting step in the heme biosynthetic pathway, with a concomitant increase in urinary and serum levels of delta-aminolevulinic acid (ALA) and porphobilonogen (PBG).
The clinical manifestation of API involves abdominal pain and a variety of neuropsychiatric and circulatory dysfunctions. As a result of the enzymatic block, heme precursors such as PBG and ALA are excreted in excess amounts in the urine and stool. In acute attacks, high levels of PGB and ALA are also found in serum. These precursors are normally undetectable in serum in healthy individuals.
The neuropsychiatric disturbances observed in these patients are thought to be due to interference of the precursors with the nervous system or due to the lack of heme. For instance, ALA bears a close resemblance to the inhibitory neurotransmitter 4-aminobutyric acid (GABA) and has been suggested to be a neurotoxin. (Jeans J. et al. 1996, American J. of Medical Genetics. 65, 269-273).
Abdominal pain is the most frequent symptom in AIP patients and occurs in more than 90% during acute attacks, which will be followed rapidly by the development of peripheral neuropathy with weakness in proximal muscles, loss of pinprick sensation, and paraesthesia. Tachycardia, obstipation or diarrhoea may also be present. During acute attacks behavioral changes, confusion, seizures, respiratory paralysis, coma and hallucinations may be present.
Hypertension is also associated with AIP, with as high as 40% of patients showing sustained hypertension between attacks. An association between chronic renal failure (Yeung L. et al. 1983, Q J. Med 52, 92-98) and AIP as well as hepatocellular carcinoma. (Lithner F. et al. 1984, Acta.Med.Scand. 215, 271-274), has been reported.
The AIP is a lifelong disease, which usually becomes manifest in puberty.
Factors Precipitating Acute Attacks
Most precipitating factors exhibit an association with the first rate-limiting enzyme in the heme biosynthetic pathway through heme, the final product of the pathway. A lowering of the heme concentration will immediately increase the rate of ALA-synthetase. An overproduction of ALA then makes the partially deficient PBGD enzyme (50% activity) now rate-limiting with an accumulation of the heme precursors ALA and PBG. Drugs that induces cytochrome P450 such as barbiturates, estrogens, sulphonamides, progesterone, carbamyazepine, and phenytoin can all precipitate acute attacks. (Wetterberg L. 1976, In Doss M. Nowrocki P. eds. Prophyrias in Human Disease. Reports of the discussion. Matgurg an der Lahn, 191-202).
The clinical manifestation is more common in women, especially at time of menstruation. Endocrine factors such as synthetic estrogens and progesterone are known precipitating factors. A significant factor is also the lack of sufficient caloric intake. Hence, caloric supplementation during acute attacks reduces clinical symptoms. (Welland, F. H. et al. 1964, Metabolism, 13, 232).
Finally, various forms of stress including illness, infection, surgery and alcoholic excess have been shown to lead to precipitation of acute attacks. There are also cases of acute attacks where no precipitating factor can be identified.
Prevalence of AIP Prevalence of 0.21% has been reported (Tishler P. V. et al. 1985, Am.J.Psychiatry 142, 1430-1436), with as high a prevalence as 1 per 1500 in geographic isolates in northern Sweden (Wetterberg L. 1967, Svenska bokfölaget Nordstedt, Stockholm). Prevalence up to 200 per 10,000 inhabitants has been reported from Arjepong in Northern Sweden (Andersson, Christer, Thesis, 1997, ISBN 91/7191/280/0, pp. 22-23).
Existing Treatment of AIP
The treatment of AIP as well as of other types of porphyrias such as variegata, hereditary coproporphyria, harderoporphyria, and aminolevulinic acid dehydratase deficiency, are basically the same. Existing therapies for AIP, are all aimed at reducing circulating PBG and ALA by inhibiting the first rate-limiting enzymatic step ALA-synthetase. This inhibition of ALA-synthetase is achieved by increasing circulating heme, since heme is a negative feed back regulator of ALA-synthetase. Hematin treatment, high caloric intake or inhibition of heme breakdown by Sn-mesoporphyrin administration are the existing therapies today. These therapies have shown limited efficacy.
Treatment between acute attacks involves sufficient caloric intake and avoidance of drugs and immediate treatment of infections.
Patients that experience acute attacks are treated with intravenous carbohydrates usually dextrose (300 g/day) and intravenous hematin (3-8 mg/(kg day)).
Treatments with long acting agonistic analogues of LHRH, have been shown to reduce the incidence of pre-menstrual attacks by inhibiting ovulation in AIP patients. Finally, treatments involving heme analogous Sn-mesoporphyrin, which inhibit heme breakdown have also been attempted.
Medical Need in AIP
The lack of effective treatment for AIP is well recognized. In a US mortality study in AIP patients requiring hospitalization it was concluded that the mortality rate was 3.2-fold higher as compared to a matched general population. Suicide was also a major cause of death, occurring at a rate of 370 times that expected in the general population (Jeans J. et al. 1996, Am. J. of Medical Genetics 65, 269-273).
Hematin therapy is usually initiated when high caloric intake is not sufficient to alleviate acute attacks. Studies with hematin have been performed but these studies generally used the patients as their own control after the patients did not respond to high ca

Affiliated with

Also associated with

Rating

Human porphobilinogen deaminase sequences does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Human porphobilinogen deaminase sequences, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Human porphobilinogen deaminase sequences will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-3013233