Alanine transaminase

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glutamic-pyruvate transaminase
Identifiers
Symbol GPT
Entrez 2875
HUGO 4552
OMIM 138200
RefSeq NM_005309
UniProt P24298
Other data
Locus Chr. 8 q24.2-qter
Alanine transaminase
Identifiers
EC number 2.6.1.2
CAS number 9000-86-6
Databases
IntEnz IntEnz view
BRENDA BRENDA entry
ExPASy NiceZyme view
KEGG KEGG entry
MetaCyc metabolic pathway
PRIAM profile
PDB structures RCSB PDB PDBe PDBsum
Gene Ontology AmiGO / EGO

Alanine transaminase (ALT) is a transaminase enzyme (EC 2.6.1.2). It is also called alanine aminotransferase (ALAT) and was formerly called serum glutamate-pyruvate transaminase (SGPT) or serum glutamic-pyruvic transaminase (SGPT).

ALT is found in plasma and in various bodily tissues, but is most commonly associated with the liver. It catalyzes the two parts of the alanine cycle.

Function[edit]

It catalyzes the transfer of an amino group from L-alanine to α-ketoglutarate, the products of this reversible transamination reaction being pyruvate and L-glutamate.

L-glutamate + pyruvate α-ketoglutarate + L-alanine
Alanine transaminase

ALT (and all transaminases) require the coenzyme pyridoxal phosphate, which is converted into pyridoxamine in the first phase of the reaction, when an amino acid is converted into a keto acid.

Clinical significance[edit]

It is commonly measured clinically as a part of a diagnostic evaluation of hepatocellular injury, to determine liver health. When used in diagnostics, it is almost always measured in international units/liter (IU/L).[1][2] While sources vary on specific reference range values for patients, 10-40 IU/L is the standard reference range for experimental studies.[1] Alanine transaminase shows a marked diurnal variation.[citation needed]

The ratio of ALT to AST (aspartate transaminase) also has clinical significance.

Elevated levels[edit]

Test results should always be interpreted using the reference range from the laboratory that produced the result. However typical reference intervals for ALT are:

Patient type Reference ranges[3]
Female ≤ 34 IU/L
Male ≤ 45 IU/L

Significantly elevated levels of ALT (SGPT) often suggest the existence of other medical problems such as viral hepatitis, diabetes, congestive heart failure, liver damage, bile duct problems, infectious mononucleosis, or myopathy, so ALT is commonly used as a way of screening for liver problems. Elevated ALT may also be caused by dietary choline deficiency. However, elevated levels of ALT do not automatically mean that medical problems exist. Fluctuation of ALT levels is normal over the course of the day, and they can also increase in response to strenuous physical exercise.[4]

When elevated ALT levels are found in the blood, the possible underlying causes can be further narrowed down by measuring other enzymes. For example, elevated ALT levels due to hepatocyte damage can be distinguished from bile duct problems by measuring alkaline phosphatase. Also, myopathy-related ALT levels can be ruled out by measuring creatine kinase enzymes. Many drugs may elevate ALT levels, including Zileuton, omega-3-acid ethyl esters (Lovaza),[5] anti-inflammatory drugs, antibiotics, cholesterol medications, some antipsychotics such as risperidone, and anticonvulsants.[citation needed]

For years, the American Red Cross used ALT testing as part of the battery of tests to ensure the safety of its blood supply by deferring donors with elevated ALT levels. The intent was to identify donors potentially infected with hepatitis C because no specific test for that disease was available at the time. Prior to July 1992, widespread blood donation testing in the USA for hepatitis C was not carried out by major blood banks. With the introduction of second-generation ELISA antibody tests for hepatitis C, the Red Cross changed the ALT policy. As of July 2003, donors previously disqualified for elevated ALT levels and no other reason may be reinstated as donors by contacting the donor-counseling department of their regional Red Cross organization.[6]

See also[edit]

References[edit]

  1. ^ a b Wang, CS; Chang, Ting-Tsung; Yao, Wei-Jen; Wang, Shan-Tair; Chou, Pesus (2012). "Impact of increasing alanine aminotransferase levels within normal range on incident diabetes". J Formos Med Assoc 111 (4): 201–8. doi:10.1016/j.jfma.2011.04.004. PMID 22526208. 
  2. ^ Ghouri, N; Preiss, David; Sattar, Naveed (2010). "Liver enzymes, nonalcoholic fatty liver disease, and incident cardiovascular disease: a narrative review and clinical perspective of prospective data". Hepatology 52 (3): 1156–61. doi:10.1002/hep.23789. PMID 20658466. 
  3. ^ "Alanine aminotransferase: analyte monograph". Association for Clinical Biochemistry and Laboratory Medicine. Retrieved 7 October 2013. 
  4. ^ Paul T. Giboney M.D., Mildly Elevated Liver Transaminase Levels in the Asymptomatic Patient, American Family Physician.
  5. ^ http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2683599/?tool=pmcentrez Omega-3-acid Ethyl Esters (Lovaza) For Severe Hypertriglyceridemia, Pharmacy and Pherapeutics.
  6. ^ Red Cross Donor Requirements

External links[edit]