Ribose-5-phosphate Isomerase Deficiency

	Ribose-5-phosphate Isomerase Deficiency Ribose-5-phosphate isomerase deficiency is a human disorder caused by mutations in ribose-5-phosphate isomerase, an enzyme of the pentose phosphate pathway. With only four diagnosed patients over a 27-year period, RPI deficiency is the second rarest disease known as of now, being beaten only by Fields Condition affecting three individuals, Catherine and Kirstie Fields, and one unknown person. Mechanism In the search for an explanation for this rarity, it has been found that the patient has a seldom-seen allelic combination. One allele is a non-functional null allele, while the other encodes for a partially active enzyme. Furthermore, the partially functional allele has expression deficits that depend on the cell type in which it is expressed. Therefore, some of the patient's cells have a considerable amount of RPI activity, whereas others do not. The molecular cause of the pathology is not fully understood. One hypothesis is that ribose-5-phosphate may be insufficient for RN ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu]
picture info	Ribose-5-phosphate Isomerase Ribose-5-phosphate isomerase (Rpi) encoded by the RPIA gene is an enzyme () that catalyzes the conversion between ribose-5-phosphate (R5P) and ribulose-5-phosphate (Ru5P). It is a member of a larger class of isomerases which catalyze the interconversion of chemical isomers (in this case structural isomers of pentose). It plays a vital role in biochemical metabolism in both the pentose phosphate pathway and the Calvin cycle. The systematic name of this enzyme class is D-ribose-5-phosphate aldose-ketose-isomerase. Structure Gene RpiA in human beings is encoded on the second chromosome on the short arm (p arm) at position 11.2. Its encoding sequence is nearly 60,000 base pairs long. The only known naturally occurring genetic mutation results in ribose-5-phosphate isomerase deficiency, discussed below. The enzyme is thought to have been present for most of evolutionary history. Knock-out experiments conducted on the genes of various species meant to encode RpiA have indicated simi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu]
	Ribitol Ribitol, or adonitol, is a crystalline pentose alcohol (C5H12O5) formed by the reduction of ribose. It occurs naturally in the plant ''Adonis vernalis'' as well as in the cell walls of some Gram-positive bacteria, in the form of ribitol phosphate, in teichoic acids. It also forms part of the chemical structure of riboflavin and flavin mononucleotide (FMN), which is a nucleotide coenzyme used by many enzymes, the so-called flavoproteins Flavoproteins are proteins that contain a nucleic acid derivative of riboflavin. Flavoproteins are involved in a wide array of biological processes, including removal of radicals contributing to oxidative stress, photosynthesis, and DNA repair. .... References External links GMD MS Spectrum [...More Info...] [...Related Items...] OR:* [Wikipedia] [Google] [Baidu]
	Leukoencephalopathy Leukoencephalopathy (leukodystrophy-like diseases) is a term that describes all of the brain white matter diseases, whether their molecular cause is known or unknown. It can refer specifically to any of these diseases: * Progressive multifocal leukoencephalopathy Toxic leukoencephalopathy Leukoencephalopathy with vanishing white matter Leukoencephalopathy with neuroaxonal spheroids Reversible posterior leukoencephalopathy syndrome Megalencephalic leukoencephalopathy with subcortical cysts. It can also refer to gene MLC1 or Megalencephalic leukoencephalopathy with subcortical cysts 1, a human gene related to the former disease. Hypertensive leukoencephalopathy The classification of leukoencephalopathies is a matter of debate. Some authors divide leukoencephalopathies into hereditary disorders and acquired disorders. The hereditary demyelinating disorders are then classified according to the localization of the underlying metabolic defect, and they include the leukodystrophies w ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu]
	Psychomotor Retardation Psychomotor may refer to: * Psychomotor learning, the relationship between cognitive functions and physical movement * Psychomotor retardation, a slowing-down of thought and a reduction of physical movements in an individual * Psychomotor agitation Psychomotor agitation is a symptom in various disorders and health conditions. It is characterized by unintentional and purposeless motions and restlessness, often but not always accompanied by emotional distress. Typical manifestations include ... , a series of unintentional and purposeless motions that stem from mental tension and anxiety of an individual {{disambiguation ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu]
	Spasticity Spasticity () is a feature of altered skeletal muscle performance with a combination of paralysis, increased tendon reflex activity, and hypertonia. It is also colloquially referred to as an unusual "tightness", stiffness, or "pull" of muscles. Clinically, spasticity results from the loss of inhibition of motor neurons, causing excessive velocity-dependent muscle contraction. This ultimately leads to hyperreflexia, an exaggerated deep tendon reflex. Spasticity is often treated with the drug baclofen, which acts as an agonist at GABA receptors, which are inhibitory. Spastic cerebral palsy is the most common form of cerebral palsy, which is a group of permanent movement problems that do not get worse over time. GABA's inhibitory actions contribute to baclofen's efficacy as an anti-spasticity agent. Cause Spasticity mostly occurs in disorders of the central nervous system (CNS) affecting the upper motor neurons in the form of a lesion, such as spastic diplegia, or upper motor neu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu]
picture info	Seizures An epileptic seizure, informally known as a seizure, is a period of symptoms due to abnormally excessive or neural oscillation, synchronous neuronal activity in the brain. Outward effects vary from uncontrolled shaking movements involving much of the body with loss of consciousness (tonic-clonic seizure), to shaking movements involving only part of the body with variable levels of consciousness (focal seizure), to a subtle momentary loss of awareness (absence seizure). Most of the time these episodes last less than two minutes and it takes some time to return to normal. Urinary incontinence, Loss of bladder control may occur. Seizures may be provoked and unprovoked. Provoked seizures are due to a temporary event such as low blood sugar, alcohol withdrawal, abusing alcohol together with prescription medication, low blood sodium, fever, brain infection, or concussion. Unprovoked seizures occur without a known or fixable cause such that ongoing seizures are likely. Unprovoked seizur ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu]
	Cerebellar Ataxia Cerebellar ataxia is a form of ataxia originating in the cerebellum. Non-progressive congenital ataxia (NPCA) is a classical presentation of cerebral ataxias. Cerebellar ataxia can occur as a result of many diseases and may present with symptoms of an inability to coordinate balance, gait, extremity and eye movements. Lesions to the cerebellum can cause dyssynergia, dysmetria, dysdiadochokinesia, dysarthria and ataxia of stance and gait. Deficits are observed with movements on the same side of the body as the lesion (ipsilateral). Clinicians often use visual observation of people performing motor tasks in order to look for signs of ataxia. Signs and symptoms Damage to the cerebellum causes impairment in motor skills and can cause nystagmus. Almost a third of people with isolated, late onset cerebellar ataxia go on to develop multiple system atrophy. The cerebellum's role has been observed as not purely motor. It is combined with intellect, emotion and planning. Cerebellar defi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu]
picture info	Nystagmus Nystagmus is a condition of involuntary (or voluntary, in some cases) eye movement. Infants can be born with it but more commonly acquire it in infancy or later in life. In many cases it may result in reduced or limited vision. Due to the involuntary movement of the eye, it has been called "dancing eyes". In normal eyesight, while the head rotates about an axis, distant visual images are sustained by rotating eyes in the opposite direction of the respective axis. The semicircular canals in the vestibule of the ear sense angular acceleration, and send signals to the nuclei for eye movement in the brain. From here, a signal is relayed to the extraocular muscles to allow one's gaze to fix on an object as the head moves. Nystagmus occurs when the semicircular canals are stimulated (e.g., by means of the caloric test, or by disease) while the head is stationary. The direction of ocular movement is related to the semicircular canal that is being stimulated. There are two key form ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu]
	Optic Atrophy Optic neuropathy is damage to the optic nerve from any cause. The optic nerve is a bundle of millions of fibers in the retina that sends visual signals to the brain. Damage and death of these nerve cells, or neurons, leads to characteristic features of optic neuropathy. The main symptom is loss of vision, with colors appearing subtly washed out in the affected eye. A pale disc is characteristic of long-standing optic neuropathy. In many cases, only one eye is affected and patients may not be aware of the loss of color vision until the doctor asks them to cover the healthy eye. Optic neuropathy is often called optic atrophy, to describe the loss of some or most of the fibers of the optic nerve. Ischemic optic neuropathy In ischemic optic neuropathies, there is insufficient blood flow (ischemia) to the optic nerve. The anterior optic nerve is supplied by the short posterior ciliary artery and choroidal circulation, while the retrobulbar optic nerve is supplied intraorbitally by ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu]
	Arabitol Arabitol, or arabinitol, is a sugar alcohol. It can be formed by the reduction of either arabinose or lyxose. Some organic acid tests check for the presence of D-arabitol, which may indicate overgrowth of intestinal microbes such as ''Candida albicans'' or other yeast/fungus A fungus ( : fungi or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and molds, as well as the more familiar mushrooms. These organisms are classified as a kingdom, separately from th ... species. References External links * Sugar alcohols {{alcohol-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu]
picture info	RNA Synthesis Transcription is the process of copying a segment of DNA into RNA. The segments of DNA transcribed into RNA molecules that can encode proteins are said to produce messenger RNA (mRNA). Other segments of DNA are copied into RNA molecules called non-coding RNAs (ncRNAs). mRNA comprises only 1–3% of total RNA samples. Less than 2% of the human genome can be transcribed into mRNA ( Human genome#Coding vs. noncoding DNA), while at least 80% of mammalian genomic DNA can be actively transcribed (in one or more types of cells), with the majority of this 80% considered to be ncRNA. Both DNA and RNA are nucleic acids, which use base pairs of nucleotides as a complementary language. During transcription, a DNA sequence is read by an RNA polymerase, which produces a complementary, antiparallel RNA strand called a primary transcript. Transcription proceeds in the following general steps: # RNA polymerase, together with one or more general transcription factors, binds to promoter DN ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu]
picture info	Enzyme Enzymes () are proteins that act as biological catalysts by accelerating chemical reactions. The molecules upon which enzymes may act are called substrates, and the enzyme converts the substrates into different molecules known as products. Almost all metabolic processes in the cell need enzyme catalysis in order to occur at rates fast enough to sustain life. Metabolic pathways depend upon enzymes to catalyze individual steps. The study of enzymes is called ''enzymology'' and the field of pseudoenzyme analysis recognizes that during evolution, some enzymes have lost the ability to carry out biological catalysis, which is often reflected in their amino acid sequences and unusual 'pseudocatalytic' properties. Enzymes are known to catalyze more than 5,000 biochemical reaction types. Other biocatalysts are catalytic RNA molecules, called ribozymes. Enzymes' specificity comes from their unique three-dimensional structures. Like all catalysts, enzymes increase the reaction ra ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu]