Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.7.7.48 (transcriptase)
 9,479 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

LALP70 is a novel lysosomal membrane protein belonging to the apyrase protein family. The apyrase protein family comprises enzymes capable of cleaving nucleotide tri- and diphosphates in a calcium- or magnesium-dependent manner, not being altered by P-type, F-type, or V-type NTPase inhibitors. In this study we have cloned and sequenced the human LALP70 gene to determine the genomic structure. The gene is organized in 11 introns and 12 exons covering a genomic region of approximately 16 kilobase pairs. By fluorescence in situ hybridization analysis, the hLALP70 gene was mapped to the human chromosome 8p21.1-p21.3. We further show that there is at least one alternatively spliced variant, hLALP70v, which can be generated via an alternative splice side at the 3'-end of exon 7, leading to a protein variant differing in 8 amino acids (VSFASSQQ). This is the first splice variant that has been described in the apyrase protein family. Reverse transcriptase polymerase chain reaction analysis showed an ubiquitous expression of both variants, with different relative mRNA expression levels in different tissues. Comparison of the enzymatic properties of the splice variants revealed a broader substrate specificity for hLALP70v with CTP, UDP, CDP, GTP, and GDP as preferred substrates, while hLALP70 utilized UTP and TTP preferentially. Furthermore, enzyme activity of hLALP70v was equally dependent on Ca(2+) and Mg(2+), being saturated already at 1 mm concentration. In contrast, hLALP70 enzymatic activity were unsaturated up to 10 mm Ca(2+), while Mg(2+) showed a saturation at already 1 mm concentration with 2-3-fold lower enzymatic activity as observed with Ca(2+). Our data suggest that the presence or absence of the 8-amino acid motif VSFASSQQ provoke differences in substrate specificity and divalent cation dependence of hLALP70/hLALP70v.
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PMID:First apyrase splice variants have different enzymatic properties. 1085 52

1. Benzodiazepines (BZ) and barbiturates both potentiate chloride currents through GABA(A) receptors to enhance inhibition. However, unlike barbiturates BZ do not impair autonomic control of heart rate. We hypothesised that BZ might not significantly potentiate GABAergic transmission in the caudal nucleus of the solitary tract (cNTS), which is critically important for mediating the baroreceptor reflex. 2. In rat brain slices the BZ agonists chlordiazepoxide and midazolam (2 and 50 microM) did not significantly enhance currents evoked by GABA in voltage-clamped cNTS neurones. Chlordiazepoxide (50 microM) reversibly increased electrically evoked IPSPs in 5/10 rostral NTS (rNTS) neurones but only in 2/10 cNTS neurones. Pentobarbitone (50-100 microM) was effective in enhancing GABA(A)-mediated responses in all NTS neurones. An inverse BZ agonist, methyl 6,7-dimethoxy-4-ethyl-beta-carboline-3-carboxylate (DMCM; 1 or 10 microM), failed to depress GABA-induced currents in the cNTS. 3. Microinjections of midazolam (10 and 100 microM solutions) into the cNTS did not affect the baroreceptor reflex (P > 0.2) while pentobarbitone (100 microM) significantly and reversibly depressed it (gain decrease to 53 +/- 11 % of control, P < 0.01). 4. Reverse transcriptase polymerase chain reaction revealed the presence of alpha(1), alpha(2), beta(2), beta(3) and gamma(2) GABA(A) receptor subunit mRNA in the cNTS. No alternatively spliced variants of the alpha(1)- and gamma(2)-subunits were revealed. Moreover, GABA(A) epsilon-unit mRNA was found in both the cNTS and rNTS as two alternatively spliced transcripts. 5. Immunocytochemical analysis revealed numerous GABA(A) epsilon-subunit-positive neurones within the cNTS with significantly fewer epsilon-subunit-positive cells in the rNTS. 6. As incorporation of the epsilon-subunit in recombinant GABA(A) receptors may confer BZ insensitivity we propose that the paucity of BZ actions in the cNTS is due to a high level of epsilon-subunit expression. This is the first demonstration of a possible physiological impact of the epsilon-subunit on native GABA(A) receptors.
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PMID:GABA(A) receptor epsilon-subunit may confer benzodiazepine insensitivity to the caudal aspect of the nucleus tractus solitarii of the rat. 1169 72