RESUMO
Shrimp lactate dehydrogenase (LDH) is induced in response to environmental hypoxia. Two protein subunits deduced from different transcripts of the LDH gene from the shrimp Litopenaeus vannamei (LDHvan-1 and LDHvan-2) were identified. These subunits are expressed by alternative splicing. Since both subunits are expressed in most tissues, the purification of the enzyme from the shrimp will likely produce hetero LDH containing both subunits. Therefore, the aim of this study was to overexpress, purify and characterize only one subunit as a recombinant protein, the LDHvan-2. For this, the cDNA from muscle was cloned and overexpressed in E. coli as a fusion protein containing an intein and a chitin binding protein domain (CBD). The recombinant protein was purified by chitin affinity chromatography column that retained the CBD and released solely the full and active LDH. The active protein appears to be a tetramer with molecular mass of approximately 140 kDa and can use pyruvate or lactate as substrates, but has higher specific activity with pyruvate. The enzyme is stable between pH 7.0 to 8.5, and between 20 and 50 °C with an optimal temperature of 50 °C. Two pKa of 9.3 and 6.6, and activation energy of 44.8 kJ/mol°K were found. The kinetic constants Km for NADH was 23.4 ± 1.8 µM, and for pyruvate was 203 ± 25 µM, while Vmax was 7.45 µmol/min/mg protein. The shrimp LDH that is mainly expressed in shrimp muscle preferentially converts pyruvate to lactate and is an important enzyme for the response to hypoxia.
Assuntos
Proteínas de Artrópodes , Expressão Gênica , L-Lactato Desidrogenase , Penaeidae/genética , Animais , Proteínas de Artrópodes/biossíntese , Proteínas de Artrópodes/química , Proteínas de Artrópodes/genética , Proteínas de Artrópodes/isolamento & purificação , Escherichia coli/genética , Escherichia coli/metabolismo , L-Lactato Desidrogenase/biossíntese , L-Lactato Desidrogenase/química , L-Lactato Desidrogenase/genética , L-Lactato Desidrogenase/isolamento & purificação , Penaeidae/enzimologia , Proteínas Recombinantes/biossíntese , Proteínas Recombinantes/química , Proteínas Recombinantes/genética , Proteínas Recombinantes/isolamento & purificaçãoRESUMO
Understanding pulp repair and regeneration requires being familiar with this tissue's behavior under extreme conditions, such as postmortem state where an abrupt interruption of tissue blood supply occurs. The purpose of this study was to quantify cell viability and the amount of lactate-dehydrogenase (LDH) expressed in human pulp tissue 6, 12, and 24 hours postmortem to establish how long dental pulp remains viable after death. Pulp samples were obtained from 14 unidentified corpses of people who had received lethal injuries in car accidents or from gunshot wounds; they had at least three caries- and restoration-free incisors. Half of each sample was used for determining cell viability at three different time intervals. The rest of each sample was used for quantifying LDH expression at the same time intervals. Another 14 pulp samples were obtained from live patients' healthy premolars where extraction was indicated for orthodontic reasons to assess normal LDH value in pulp tissue. The results showed cell viability decreasing from 89 to 68 to 41% measured 6, 12, and 24 hours postmortem, respectively. LDH expression in healthy pulps was 246 U/mg pulp weight. Expression increased after death from 249 U/mg at 6 hours to 337 U/mg at 12 hours. LDH expression decreased to 131 U/mg 24 hours postmortem. These findings are valuable in understanding dental pulp survival capability under extreme conditions that may have important clinical significance in terms of repair and regeneration.
Assuntos
Polpa Dentária/enzimologia , Mudanças Depois da Morte , Análise de Variância , Sobrevivência Celular , Polpa Dentária/citologia , Humanos , L-Lactato Desidrogenase/biossíntese , Fatores de TempoRESUMO
A comparative study of proteinograms and zymograms (LDH, MDH) has been carried out at different ontogenic stages, in Ambystoma mexicanum (A.m.), Ambystoma dumerilii (A.d.) and nucleocytoplasmic hybrids 2 n A.d/cytoplasm Am. It appears that 2 n A.d. nucleus, grafted in A.m. cytoplasm expresses only a part of its potentialities, which could account for lethality of the nucleocytoplasmic hybrids.