Correlation between R/S enantiomer ratio of lansoprazole and CYP2C19 activity after single oral and enteral administration

The purpose of this study was to investigate whether CYP2C19 activity can be estimated from plasma concentrations of lansoprazole enantiomers 4 h (C_4h) after single administration by oral and enteral routes. Sixty‐nine subjects, 22 homozygous extensive metabolizers (homEMs), 32 heterozygous EMs (hetEMs), and 15 poor metabolizers (PMs), participated in the study. After a single oral or enteral dose of racemic lansoprazole (30 mg), plasma concentrations of lansoprazole enantiomers were measured 4 h postdose. The R/S ratio of lansoprazole at 4 h differed significantly among the three groups (P < 0.0001) regardless of the administration route. The R/S ratio of lansoprazole in CYP2C19 PMs ranged from 3.0 to 13.7, whereas in homEMs and hetEMs the ratio ranged from 8.6 to 90 and 2.1 to 122, respectively. The relationship between (S)‐lansoprazole concentration and R/S ratio of lansoprazole at C_4h is given by the following formula: log₁₀ [R/S ratio] = 2.2 – 0.64 × log₁₀ [C_4h of (S)‐lansoprazole] (r = 0.867, P < 0.0001). Thus, phenotyping CYP2C19 using the R/S enantiomer ratio of lansoprazole seems unlikely. However, to obtain a pharmacological effect similar to that in CYP2C19 PMs, we can presume that lansoprazole has a sufficient effect in the patient with an R/S enantiomer ratio at 4 h ≤ 13.70 and (S)‐lansoprazole concentration at 4 h ≥ 50 ng/ml. Chirality 2010. © 2009 Wiley‐Liss, Inc.     

Expression,localization, and biological function of the R3 subtype of receptor-type protein tyrosine phosphatases in mammals

The R3 subtype of receptor-type protein tyrosine phosphatases (RPTPs) includes VE-PTP, DEP-1, PTPRO, and SAP-1. All of these enzymes share a similar structure, with a single catalytic domain and putative tyrosine phosphorylation sites in the cytoplasmic region and fibronectin type III–like domains in the extracellular region. The expression of each R3 RPTP is largely restricted to a single or limited number of cell types, with VE-PTP and DEP-1 being expressed in endothelial or hematopoietic cells, PTPRO in neurons and in podocytes of the renal glomerulus, and SAP-1 in gastrointestinal epithelial cells. In addition, these RPTPs are localized specifically at the apical surface of polarized cells. The structure, expression, and localization of the R3 RPTPs suggest that they perform tissue-specific functions and that they might act through a common mechanism that includes activation of Src family kinases. In this review, we describe recent insights into R3-subtype RPTPs, particularly those of mammals.     

Replacement of C305 in Heart/Muscle-Type Isozyme of Human Carnitine Palmitoyltransferase I with Aspartic Acid and Other Amino Acids

Liver- and heart/muscle-type isozymes of human carnitine palmitoyltransferase I (L- and M-CPTI, respectively) show a certain similarity in their amino acid sequences, and mutation studies on the conserved amino acids between these two isozymes often show essentially the same effects on their enzymatic properties. Earlier mutation studies on C305 in human M-CPTI and its counterpart residue, C304, in human L-CPTI showed distinct effects of the mutations, especially in the aspect of enzyme stability; however, simple comparison of these effects on the conserved Cys residue between L- and M-CPTI was difficult, because these studies were carried out using different expression systems and distinct amino acids as replacements. In the present study, we carried out mutation studies on the C305 in human M-CPTI using COS cells for the expression system. Our results showed that C305 was replaceable with aspartic acid but that substitution with other amino acids caused both loss of function and reduced expression.     

Parasporin-2Ab,a Newly Isolated Cytotoxic Crystal Protein from <Emphasis Type="Italic">Bacillus thuringiensis</Emphasis>

A novel crystal protein that exhibited potent cytotoxicity against human leukemic T-cells was cloned from the Bacillus thuringiensis TK-E6 strain. The protein, designated as parasporin-2Ab (PS2Ab), was a polypeptide of 304 amino acid residues with a predicted molecular weight of 33,017. The deduced amino acid sequence of PS2Ab showed significant homology (84% identitiy) to parasporin-2Aa (PS2Aa) from the B. thuringiensis A1547 strain. Upon processing of PS2Ab with proteinase K, the active form of 29 kDa was produced. The activated PS2Ab showed potent cytotoxicity against MOLT-4 and Jurkat cells and the EC₅₀ values were estimated as 0.545 and 0.745 ng/mL, respectively. The cytotoxicity of PS2Ab was significantly higher than that of PS2Aa reported elsewhere. Although both cytotoxins were structurally related, it was thought that the minor differences found were responsible for the different cytotoxicities of PS2Ab and PS2Aa.     

Sugar-inducible expression of the nucleolin-1 gene of Arabidopsis thaliana and its role in ribosome synthesis, growth and development

Animal and yeast nucleolin function as global regulators of ribosome synthesis, and their expression is tightly linked to cell proliferation. Although Arabidopsis contains two genes for nucleolin, AtNuc-L1 is the predominant if not only form of the protein found in most tissues, and GFP-AtNuc-L1 fusion proteins were targeted to the nucleolus. Expression of AtNuc-L1 was strongly induced by sucrose or glucose but not by non-metabolizable mannitol or 2-deoxyglucose. Sucrose also caused enhanced expression of genes for subunits of C/D and H/ACA small nucleolar ribonucleoproteins, as well as a large number of genes for ribosomal proteins (RPs), suggesting that carbohydrate availability regulates de novo ribosome synthesis. In sugar-starved cells, induction of AtNuc-L1 occurred with 10 mM glucose, which seemed to be a prerequisite for resumption of growth. Disruption of AtNuc-L1 caused an increased steady-state level of pre-rRNA relative to mature 25S rRNA, and resulted in various phenotypes that overlap those reported for several RP gene mutants, including a reduced growth rate, prolonged lifetime, bushy growth, pointed leaf, and defective vascular patterns and pod development. These results suggest that the rate of ribosome synthesis in the meristem has a strong impact not only on the growth but also the structure of plants. The AtNuc-L1 disruptant exhibited significantly reduced sugar-induced expression of RP genes, suggesting that AtNuc-L1 is involved in the sugar-inducible expression of RP genes.     

Novel and potent calcium-sensing receptor antagonists: discovery of (5R)-N-[1-ethyl-1-(4-ethylphenyl)propyl]-2,7,7-trimethyl-5-phenyl-4,5,6,7-tetrahydropyrazolo[1,5-a]pyrimidine-3-carboxamide monotosylate (TAK-075) as an orally active bone anabolic agent

The calcium-sensing receptor antagonist (CaSR) has been recognized as a promising target of anabolic agents for treating osteoporosis. In the course of developing a new drug candidate for osteoporosis, we found tetrahydropyrazolopyrimidine derivative 1 to be an orally active CaSR antagonist that stimulated transient PTH secretion in rats. However, compound 1 showed poor physical and chemical stability. In order to work out this compound's chemical stability and further understand its in vivo efficacy, we focused on modifying the 2-position of the tetrahydropyrazolopyrimidine. As a result of chemical modification, we discovered (5R)-N-[1-ethyl-1-(4-ethylphenyl)propyl]-2,7,7-trimethyl-5-phenyl-4,5,6,7-tetrahydropyrazolo[1,5-a]pyrimidine-3-carboxamide monotosylate 10m (TAK-075), which showed improved solubility, chemical stability, and in vivo efficacy. Furthermore, we describe that evaluating the active metabolite is important during repeated treatment with short-acting CaSR antagonists.