Serum Enzyme Levels in Diagnosis of Postoperative Myocardial Infarction

The levels of creatine kinase, hydroxybutyric dehydrogenase, and aspartate transaminase have been serially measured in the serum of patients undergoing surgery. Serum enzyme levels often rose to a range commonly found after myocardial infarction but fell to normal within 5-10 days. Raised serum enzyme levels have no diagnostic significance in a case of postoperative chest pain until after the fifth postoperative day, but may be significant thereafter.     

Interpretation of Serum Creatine Kinase in Suspected Myocardial Infarction

Serum creatine kinase (CK) was measured in blood donors, patients admitted to hospital with suspected myocardial infarction, and healthy hospital personnel to investigate the normal range, the daily variation in healthy people, and the effect of intramuscular injections of pentazocine or diamorphine.There was considerable daily variation in the healthy controls, apparently related to exercise. In defining both the normal range and the significance of day-to-day increases in the serum CK account should be taken of this factor. An upper limit of normal of 210 IU/1. Should apply to previously ambulant patients and of 165 IU/1. to patients previously at rest. An increase greater than 85% in successive daily values is uncommon in health.Intramuscular injections of both pentazocine and diamorphine caused a significant rise in the serum CK in six out of 25 patients. The highest rise observed was from 64 IU/1. to 395 IU/1. Caution is therefore urged in the diagnosis of myocardial infarction from the serum CK values when these intramuscular injections have been given.     

Specificity of Serum Creatine Kinase Isoenzymes in Diagnosis of Acute Myocardial Infarction

A study of the diagnostic value of serum creatine kinase (CK) isoenzymes showed that MB isoenzyme, which characterizes heart tissue, was a specific and sensitive indicator of acute myocardial infarction. In cases where the clinical picture was complicated by ventricular tachycardia, severe congestive failure, shock, or resuscitation procedures heart, liver, and muscle enzymes were increased. There was also an increase in lactate dehydrogenase isoenzyme values in these cases; indeed, the only enzyme test that correlated well with electrocardiographic and necropsy findings was the MB isoenzyme.     

Metabolite Profiling Reveals YihU as a Novel Hydroxybutyrate Dehydrogenase for Alternative Succinic Semialdehyde Metabolism in Escherichia coli

The search for novel enzymes and enzymatic activities is important to map out all metabolic activities and reveal cellular metabolic processes in a more exhaustive manner. Here we present biochemical and physiological evidence for the function of the uncharacterized protein YihU in Escherichia coli using metabolite profiling by capillary electrophoresis time-of-flight mass spectrometry. To detect enzymatic activity and simultaneously identify possible substrates and products of the putative enzyme, we profiled a complex mixture of metabolites in the presence or absence of YihU. In this manner, succinic semialdehyde was identified as a substrate for YihU. The purified YihU protein catalyzed in vitro the NADH-dependent reduction of succinic semialdehyde to γ-hydroxybutyrate. Moreover, a yihU deletion mutant displayed reduced tolerance to the cytotoxic effects of exogenous addition of succinic semialdehyde. Profiling of intracellular metabolites following treatment of E. coli with succinic semialdehyde supports the existence of a YihU-catalyzed reduction of succinic semialdehyde to γ-hydroxybutyrate in addition to its known oxidation to succinate and through the tricarboxylic acid cycle. These findings suggest that YihU is a novel γ-hydroxybutyrate dehydrogenase involved in the metabolism of succinic semialdehyde, and other potentially toxic intermediates that may accumulate under stress conditions in E. coli.The search for novel enzymes is important to better our understanding of the metabolic systems of the cell. Although computational tools can be used to functionally annotate enzymes based on sequence homology, gene structure and expression, and prediction of enzyme-like domains, the identification of the exact physiological substrates remains difficult when sequence similarity to known enzymes is low (<60%) and requires experimental confirmation (1, 2). Consequently, many gaps remain in metabolic pathways even in the model microorganism Escherichia coli (3, 4). Moreover, the identification of dispensable enzymatic activities, such as metabolic bypass pathways or the characterization of enzymes that are expressed only under specific physiological conditions, is particularly challenging.The β-hydroxyacid dehydrogenase enzyme family is a structurally conserved group of enzymes that include β-hydroxyisobutyrate dehydrogenase, 6-phosphogluconate dehydrogenase, and numerous uncharacterized homologs (5, 6). This enzyme family contains well conserved domains in its sequence that include a N-terminal Rossmann-fold characteristic of a dinucleotide binding site, a well defined sequence at the substrate binding site, and a conserved lysine residue proposed as a critical catalytic residue. This last specific structural feature has been proposed based on site-directed mutagenesis and x-ray crystal structures (6, 7). The E. coli K12 proteome appears to contain four β-hydroxyacid dehydrogenase paralogs. The product of the glxR gene has been identified as tartronate semialdehyde reductase, catalyzing the NAD⁺-dependent oxidation of d-glycerate and the NADH-dependent reduction of tartronate semialdehyde (8). This enzyme plays a role in allantoin utilization under anaerobic conditions in E. coli (9). However, the function of the other three representatives of the family remains unknown.Under aerobic conditions in E. coli, γ-aminobutyrate (GABA)² is metabolized via GABA transaminase (EC 2.6.1.19) (10) and oxidized to succinate by at least two different succinic semialdehyde dehydrogenases (EC 1.2.1.16 and EC 1.2.1.24) (11, 12), and then further metabolized in the tricarboxylic acid cycle. In some animals (13), plants (14), and bacterial species (15, 16), γ-hydroxybutyrate (GHB) can be produced during GABA catabolism through the reduction of succinic semialdehyde (SSA) under anaerobic conditions. A γ-hydroxybutyrate dehydrogenase (GHBDH) was recently identified in Arabidopsis thaliana (14). Interestingly, the Arabidopsis enzyme does not show significant homology with known GHBDHs, however, its sequence exhibits similarity to several dehydrogenases including β-hydroxyacid dehydrogenases and 6-phosphogluconate dehydrogenases. However, the existence of an equivalent of the GHBDH reaction and an alternative reductive pathway for GABA metabolism in E. coli is still unreported.We have previously developed a screening method, based on in vitro assays in combination with metabolite profiling by capillary electrophoresis-mass spectrometry (CE-MS), to discover novel enzymatic activities (17). We hereby refer to this method as Metabolic Enzyme and Reaction discovery by Metabolite profile Analysis and reactant IDentification (MERMAID). Using this method, the enzymatic activity of any uncharacterized protein can be tested in an unbiased way by monitoring changes in a complex metabolite mixture that are induced by the test protein. This can allow to directly determine the substrate(s) and/or product(s) of the reaction without designing specific assays. Compounds whose levels specifically decrease following incubation with a protein are likely substrates, whereas metabolites whose level increase during the incubation are likely products of the reaction. In this study, we screened the E. coli YihU protein using the MERMAID approach and observed that it displays reductase activity toward short chain aldehydes, predominantly toward SSA. This activity differs from that of the known β-hydroxyacid dehydrogenases. We further demonstrate the presence of an alternative reaction for SSA catabolism leading to the production of GHB in E. coli.     

血清CREG蛋白在急性心肌梗死早期的表达研究

目的：探讨血清中CREG蛋白在急性心肌梗死发作早期的表达情况,尝试为临床心肌缺血的极早期诊断提供一种新的血清标志分子。方法：在2010年6月至2010年11月期间,入选在沈阳军区总医院心内科住院治疗的急性ST段抬高型心肌梗死患者50例及非AMI对照50例,于AMI组胸痛发作后的不同时间点采血测定CK、CK—MB、LDH和cTnT,同时应用Westem blot技术测定血清中CREG蛋白的含量,并与对照组比较。结果：AMI组发病72小时内的血清中CREG蛋白表达均较对照组有不同程度的增高（P〈0．05）。胸痛开始2h内,AMI组血清中CREG的含量即明显增高,其在2h、4h及6h的含量显著高于对照组（P〈0．001）。在胸痛已经发作2小时内,两组间血清cTnT、CK、CK-MB及LDH水平比较无统计学意义（P〉0．05）。结论：CREG在AMI患者血清中的表达增高．其在血清中表达时间早于cTNT及CK-MB。     

血清CREG蛋白在急性心肌梗死早期的表达研究

目的:探讨血清中CREG蛋白在急性心肌梗死发作早期的表达情况,尝试为临床心肌缺血的极早期诊断提供一种新的血清标志分子。方法:在2010年6月至2010年11月期间,入选在沈阳军区总医院心内科住院治疗的急性ST段抬高型心肌梗死患者50例及非AMI对照50例,于AMI组胸痛发作后的不同时间点采血测定CK、CK-MB、LDH和cTnT,同时应用Western blot技术测定血清中CREG蛋白的含量,并与对照组比较。结果:AMI组发病72小时内的血清中CREG蛋白表达均较对照组有不同程度的增高(P<0.05)。胸痛开始2h内,AMI组血清中CREG的含量即明显增高,其在2h、4h及6h的含量显著高于对照组(P<0.001)。在胸痛已经发作2小时内,两组间血清cTnT、CK、CK-MB及LDH水平比较无统计学意义(P>0.05)。结论:CREG在AMI患者血清中的表达增高,其在血清中表达时间早于cTNT及CK-MB。