Constant-proportion groups of multilocated enzymes

Pette, Dirk; Luh, Wilfried

doi:10.1016/0006-291x(62)90279-6

Cited by 62 publications

(6 citation statements)

References 10 publications

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“…The very first indication that ALT exists in the mitochondria came from Hird and Rowsell who reported alanine aminotransferase activity in the soluble phase and particulate fraction of rat homogenates (22). Since then, other studies found ALT activity in the mitochondria of rat, pig, guinea pig, chicken and insects (20,23). Furthermore, proven localisation of ALT2 in the mitochondria in the liver of gilthead sea bream (Sparus aurata) was previously reported (24).…”

Section: Discussionmentioning

confidence: 96%

Detection of the mitochondrial and catalytically active alanine aminotransferase in human tissues and plasma

Glinghammar

Rafter²,

Lindström³

et al. 2009

Int J Mol Med

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Abstract. Serum alanine aminotransferase (ALT) is used as a clinical marker of hepatotoxicity. Three forms of human ALT have been identified, ALT1 and 2 and an alternative splice variant of ALT2 (herein called ALT2_2). The standard ALT activity assay does not discriminate between ALT from different organs, or the isoforms measured in the plasma. Here, we show that ALT1 and 2 possess similar enzymatic activity for alanine and pyruvate but with different K m and k cat values, while recombinant ALT2_2 protein does not possess any enzymatic activity. Isolation of organelles from cultured human skeletal muscle cells, showed localisation of ALT2 to the mitochondrial fraction and endoplasmatic reticulum (ER), but not to the cytosol. In human hepatocytes, on the other hand, ALT1 was only localised to the cytosol and ER, with no detection in mitochondria. ALT2 was not detected in cultured human hepatocytes, liver extract or tissue using Western blotting or immunohistochemistry. The islet of Langerhans and cardiomyocytes were other examples of cells with high expression of catalytic ALT2. A clinical method for selective measurement of ALT1 and 2 in human plasma is described, and both ALT1 and 2 were immunoprecipitated from human plasma and structurally detected using Western blotting techniques.

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Section: Discussionmentioning

confidence: 96%

Detection of the mitochondrial and catalytically active alanine aminotransferase in human tissues and plasma

Glinghammar

Rafter²,

Lindström³

et al. 2009

Int J Mol Med

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“…Yang et al (3) mapped another human ALT isozyme (GPT2), to chromosome 16q12.1. These respective proteins are both functional enzymes but with different cellular locations, with the ALT1 protein being present in the cytoplasm and the ALT2 protein in the mitochondria (5)(6)(7)(8)(9)(10)(11).…”

Section: Introductionmentioning

confidence: 99%

Isoform-specific alanine aminotransferase measurement can distinguish hepatic from extrahepatic injury in humans

Rafter

Gråberg

Kotronen

et al. 2012

International Journal of Molecular Medicine

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Abstract. Serum alanine aminotransferase (ALT) is used as a clinical marker to detect hepatic damage and hepatoxicity. Two isoforms of ALT have been identified, ALT1 and ALT2, which have identical enzymatic capacities and are detected simultaneously in human serum/plasma using classical clinical chemical assays. Differences exist in the expression patterns of the ALT1 and ALT2 proteins in different organs which suggest that changes in the proportion of ALT1 and ALT2 in plasma may arise and reflect damage to different human organs. However, this has not been previously studied due to the lack of a selective methodology that can quantify both ALT1 and ALT2 isoforms in the total ALT activity normally measured in clinical samples. To the best of our knowledge, our current study reveals for the first time, that under 3 different conditions of liver damage (non-alcoholic fatty liver disease, hepatitis C and during liver surgery) the leakage of ALT1 activity into plasma greatly exceeds that of ALT2, and that the measurement of ALT1 during liver damage is equal to the measurement of total ALT activity. By contrast, during skeletal muscle injury, induced in volunteers by physical exertion, the leakage of ALT2 exceeds that of ALT1 and the proportion of circulating ALT isoforms changes accordingly. The ALT isoform changes occurring in plasma reflect previously demonstrated relative contents of ALT1 and ALT2 activities in human liver and skeletal muscle. These data suggest that assessing the percentage contribution of ALT1 and ALT2 activities to total ALT activity in plasma may distinguish hepatic from extrahepatic injury using the same standard analytical platform.

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“…According to Laudahn et al, (1968), the average of GOT and GPT activities is significantly higher in human trunk muscles than in the extremities muscles. The level of GOT activity is higher in the flight muscle of Locusta migratoria than in the flexor tibis muscle of this insect (Pette et al, 1962).…”

Section: Discussionmentioning

confidence: 65%

Transaminases of Skeletal Muscle. 2. Transaminase Activities in White and Red Muscles of Pigs and Cows

Hamm¹

1969

Journal of Food Science

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SUMMARY: The total activity of glutamic‐oxaloacetic transaminase (GOT). the relative activity of the mitochondrial GOT isozyme (GOTM) and the total activity of glutamic‐pyruvic transaminase (GPT) in five different muscles of four pigs and two cows were determined. A highly significant, positive correlation was found between either GOT or GPT activity and the amount of muscle pigments. Tonic “red”) (muscles had high transaminase activities and tetanic (“white”) muscles had low transaminase activities. However, the relative GOTm activity (GOTM activity in percent of the totaf GOT activity) of porcine muscle was found to be almost constant in the different types of muscle. Likewise, in bovine muscles, higher GOT and GPT activities were found in “red” than in “white” muscles. However, the relative GOTK activity seemed to be higher in the “red” than in the “white” muscles. A discussion of the transaminase activities and their relationship to muscle function is presented.

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Constant-proportion groups of multilocated enzymes

Cited by 62 publications

References 10 publications

Detection of the mitochondrial and catalytically active alanine aminotransferase in human tissues and plasma

Detection of the mitochondrial and catalytically active alanine aminotransferase in human tissues and plasma

Isoform-specific alanine aminotransferase measurement can distinguish hepatic from extrahepatic injury in humans

Transaminases of Skeletal Muscle. 2. Transaminase Activities in White and Red Muscles of Pigs and Cows

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