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Metabolism
Published in Peter Kam, Ian Power, Michael J. Cousins, Philip J. Siddal, Principles of Physiology for the Anaesthetist, 2020
Peter Kam, Ian Power, Michael J. Cousins, Philip J. Siddal
The catabolism of amino acids involves oxidative deamination. The first step involves transamination where the amino group is removed, leaving a carbon moiety. The amino groups pass through several amino acids and finally form glutamate and aspartate. The glutamate is converted to ammonia by glutamate dehydrogenase. Ammonia, together with aspartate and CO2, enters the urea cycle to form urea, utilizing two ATPs (Figure 65.8).
Metabolism, nutrition, exercise and temperature regulation
Published in Peter Kam, Ian Power, Michael J. Cousins, Philip J. Siddal, Principles of Physiology for the Anaesthetist, 2015
Peter Kam, Ian Power, Michael J. Cousins, Philip J. Siddal
The catabolism of amino acids involves oxidative deamination. The first step involves transamination where the amino group is removed, leaving a carbon moiety. The amino groups pass through several amino acids and finally form glutamate and aspartate. The glutamate is converted to ammonia by glutamate dehydrogenase. Ammonia, together with aspartate and CO2, enters the urea cycle to form urea, utilizing two ATPs (Figure 12.8).
Macronutrients
Published in Chuong Pham-Huy, Bruno Pham Huy, Food and Lifestyle in Health and Disease, 2022
Chuong Pham-Huy, Bruno Pham Huy
Some enzymes are used as markers for the diagnosis of disease. Some enzymes are found only in specific tissues or in a limited number of such tissues (54). For example, lactase dehydrogenase (LDH) is only found in heart and skeletal muscle. An increase of any form of LDH in the blood indicates some kind of tissue damage. A heart attack can usually be diagnosed with certainty if there is an increase of LDH from heart. Also, Creatine Kinase (CK), also called creatine phosphokinase (CPK), is an enzyme that occurs in the brain, heart, and skeletal muscle. An elevated level of creatinine kinase can indicate a stroke, a brain tumor, or a heart attack. After a heart attack, CPK shows up more rapidly in the blood than LDH. Monitoring the presence of both enzymes extends the possibility of diagnosis, which is useful, since a very mild heart attack might be difficult to diagnose (54). LDH is also a valuable prognostic marker in lymphoma, leukemia, and colon cancer (56). Another useful enzyme assayed is acetyl cholinesterase, which is important in controlling certain nerve impulses. Many pesticides affect this enzyme, so farm workers are often tested to be sure that they have not received inappropriate exposure to these important agricultural toxins (54). There are several enzymes that are typically used in the clinical laboratory to diagnose diseases. Commonly assayed enzymes frequently used in diagnosis of heart, liver or brain are the amino transferases including alanine transaminase (ALT), also named serum glutamate-pyruvate aminotransferase (SGPT), and aspartate aminotransferase (AST) or serum glutamate-oxaloacetate aminotransferase (SGOT). SGPT can be found in the liver, skeletal muscle and heart, and its high level in serum is a specific indicator of liver damage. SGOT is a marker of heart attack, while SGPT is an indicator of hepatic diseases (54, 56). In humans, high level of alkaline phosphatase (ALP) indicates an increased osteoblastic activity, as in some bone diseases such as rheumatoid arthritis, rickets, osteomalacia, hyperthyroidism, hyperparathyroidism, and also in hepatobiliary pathology (54, 56). The acid phosphatase (ACP) level found in male prostate gland is 100 times more than in erythrocytes and other body tissue (56). ACP is used in diagnosis of prostate carcinoma (54, 56). ACP assay is supplemented by the prostate specific antigen (PSA) test (56). Glutamate dehydrogenase (GLDH), present in the liver, is used to detect hepatic parenchymal disease. Aldolase (ALD), found in skeletal muscle and the heart, is involved in muscle disease (54). In humans, creatine kinase (CK) is associated with myocardial infarction and muscle diseases (54, 56). Other enzymes are assayed under a variety of different clinical situations. Since these enzymes are relatively easy to determine with precision using automated techniques, they are part of the standard blood test for the rapid diagnosis and treatment of many diseases.
A potential role of Sirtuin3 and its target enzyme activities in patients with ovarian endometrioma
Published in Gynecological Endocrinology, 2021
İslim Kaleler, Abdullah Serdar Acikgoz, Altay Gezer, Ezel Uslu
Glutamate dehydrogenase (GDH) is the key regulator of mitochondrial metabolism. It contributes to energy production, cell signal, and redox homeostasis by playing a central role in connecting glutamate to the tricarboxylic acid (TCA) cycle [8]. Succinate dehydrogenase (SDH) participates in the TCA cycle and oxidative phosphorylation, and it has important functions both in metabolism and in mediating reactive oxygen species (ROS) formation [9]. Loss of SDH activity causes accumulation of succinate in the cell. Increased succinate in the cell plays a role in many biological processes such as metastasis, invasion, and angiogenesis, especially in cancer. It has been reported that both SDH enzyme and succinate can be used as diagnostic markers in various cancers [10]. Reversible acetylation of SDH and GDH enzymes by SIRT3-dependent deacetylase enhances their activity [11,12]. SIRT3 deficiency leads to higher glycolytic activity as well as a dysfunctional electron transport chain (ETC) [13,14]
Advances and required improvements in methods to diagnosing Clostridioides difficile infections in the healthcare setting
Published in Expert Review of Molecular Diagnostics, 2021
Masako Mizusawa, Karen C Carroll
The reference methods of C. difficile testing are toxigenic culture (TC) and cell culture cytotoxicity neutralization assay (CCNA). They are labor-intensive and time-consuming tests that require technical expertise and therefore are no longer used for routine diagnostic testing for C. difficile in clinical microbiology laboratories. Glutamate dehydrogenase (GDH) is an enzyme that is produced by all C. difficile strains regardless of toxigenicity. Enzyme immunoassay (EIA) detection of GDH is a rapid test with high sensitivity and specificity [72] and it is used as an initial screening test for presence of C. difficile in the stool specimens. Toxin EIA and nucleic acid tests are the main methods used in the current laboratory diagnostic algorithms for CDI [73].
Biomarkers of drug-induced liver injury: progress and utility in research, medicine, and regulation
Published in Expert Review of Molecular Diagnostics, 2018
Mitchell R. McGill, Hartmut Jaeschke
Glutamate dehydrogenase (GLDH) is an enzyme present in the mitochondrial matrix of most eukaryotic cells. In humans, its expression is highest in liver tissue [74], and it is concentrated in the centrilobular area within the liver [75]. Although it is also expressed in the kidney, expression is much higher in the liver [74,76]. GLDH is important for amino acid metabolism, the urea cycle and the Krebs cycle. It catalyzes the reversible deamination of glutamate to α-ketoglutarate and ammonia. The α-ketoglutarate can then feed into the Krebs cycle, or it can be used by aminotransferases to make pyruvate and re-synthesize glutamate, while ammonia proceeds to urea synthesis for excretion. The reaction catalyzed by GLDH also produces NADH, which can be used in numerous other reactions including ATP synthesis through the electron transport chain. The enzyme can be measured in plasma using spectrophotometry based on its reverse reaction that consumes NADH [50].