To determine the enzymatic function of the starch-related R1 protein it was heterologously expressed in Escherichia coli and purified to apparent homogeneity. Incubation of the purified protein with various phosphate donor and acceptor molecules showed that R1 is capable of phosphorylating glucosyl residues of ␣-glucans at both the C-6 and the C-3 positions in a ratio similar to that occurring naturally in starch. Phosphorylation occurs in a dikinase-type reaction in which three substrates, an ␣-polyglucan, ATP, and H2O, are converted into three products, an ␣-polyglucan-P, AMP, and orthophosphate. The use of ATP radioactively labeled at either the ␥ or ␤ positions showed that solely the ␤ phosphate is transferred to the ␣-glucan. The apparent Km of the R1 protein for ATP was calculated to be 0.23 M and for amylopectin 1.7 mg⅐ml ؊1 . The velocity of in vitro phosphorylation strongly depends on the type of the glucan. Glycogen was an extremely poor substrate; however, the efficiency of phosphorylation strongly increased if the glucan chains of glycogen were elongated by phosphorylase. Mg 2؉ ions proved to be essential for activity. Incubation of R1 with radioactively labeled ATP in the absence of an ␣-glucan showed that the protein phosphorylates itself with the ␤, but not with the ␥ phosphate. Autophosphorylation precedes the phosphate transfer to the glucan indicating a ping-pong reaction mechanism.S tarch is the storage carbohydrate most widely distributed in the plant kingdom. In storage organs it serves as a long-term carbon reserve, whereas in photosynthetically competent tissues it is transiently accumulated to provide both reduced carbon and energy during periods unfavorable for photosynthesis. Starch consists of essentially linear (amylose) and highly branched (amylopectin) glucose polymers that are arranged as semicrystalline particles, the starch granules. Amylopectin from many sources contains phosphate-monoesters that are covalently bound at the C6 and C3 positions of the glucosyl residues (1). In potato tuber starch Ϸ0.1-0.5% of the glucose moieties are phosphorylated. The amount of phosphate monoesters in starch strongly influences its physicochemical properties (2) and, therefore, affects the ability of different starches to be used by industry.In potato tubers the starch-bound phosphate comprises a significant proportion of the total tuber phosphate content, but its function in starch metabolism is not clear. The same holds true for the biochemical reaction(s) leading to the formation of the starch phosphate monoesters. A protein (designated as R1) has been recently identified using a proteomic approach, and circumstantial evidence suggests that it is involved in the phosphorylation of starch (2, 3). The C-terminal sequence of the R1 protein shows some homology to bacterial PEP synthases (pyruvate, water dikinase EC 2.7.9.2), which transfer phosphate from ATP in a dikinase reaction to pyruvate and water. Antisense repression of R1 in potato leads to a strong reduction in the amount of starch-boun...

It is known that co‐administration of CYP3A inducers may decrease the effectiveness of oral contraceptives containing progestins as mono‐preparations or combined with ethinylestradiol. In a randomized clinical drug‐drug interaction study, we investigated the effects of CYP3A induction on the pharmacokinetics of commonly used progestins and ethinylestradiol. Rifampicin was used to induce CYP3A. The progestins chosen as victim drugs were levonorgestrel, norethindrone, desogestrel, and dienogest as mono‐products, and drospirenone combined with ethinylestradiol. Postmenopausal women (n = 12–14 per treatment group) received, in fixed sequence, a single dose of the victim drug plus midazolam without rifampicin, with rifampicin 10 mg/day (weak induction), and with rifampicin 600 mg/day (strong induction). The effects on progestin exposure were compared with the effects on midazolam exposure (as a benchmark). Unbound concentrations were evaluated for drugs binding to sex hormone binding globulin. Weak CYP3A induction, as confirmed by a mean decrease in midazolam exposure by 46%, resulted in minor changes in progestin exposure (mean decreases: 15–37%). Strong CYP3A induction, in contrast, resulted in mean decreases by 57–90% (mean decrease in midazolam exposure: 86%). Namely, the magnitude of the observed induction effects varied from weak to strong. Our data might provide an impetus to revisit the currently applied clinical recommendations for oral contraceptives, especially for levonorgestrel and norethindrone‐containing products, and they might give an indication as to which progestin could be used, if requested, by women taking weak CYP3A inducers—although it is acknowledged that the exact exposure‐response relationship for contraceptive efficacy is currently unclear for most progestins.

This first-in-human study investigated the safety, tolerability, metabolism, pharmacokinetics, biodistribution, and radiation dosimetry of 68 Ga-bombesin antagonist 68 Ga-DOTA-4-amino-1-carboxymethylpiperidine-D-Phe-Gln-Trp-Ala-Val-Gly-His-Sta-Leu-NH 2 . Methods: Five healthy men underwent dynamic whole-body PET/CT after an intravenous injection of BAY 86-7548 (138 6 5 MBq). Besides total radioactivity, plasma samples were analyzed by radio-high-performance liquid chromatography for metabolism of the tracer. Dosimetry was calculated using the OLINDA/EXM software. Results: Three radioactive plasma metabolites were detected. The proportion of unchanged BAY 86-7548 decreased from 92% 6 9% at 1 min after injection to 19% 6 2% at 65 min. The organs with the highest absorbed doses were the urinary bladder wall (0.62 mSv/MBq) and the pancreas (0.51 mSv/MBq). The mean effective dose was 0.051 mSv/MBq. BAY 86-7548 was well tolerated by all subjects. Conclusion: Intravenously injected BAY 86-7548 is safe, and rapid metabolism is demonstrated. A 150-MBq injection of BAY 86-7548 results in an effective dose of 7.7 mSv, which could be reduced to 5.7 mSv with frequent bladder voids.Key Words: dosimetry; 68 Ga; PET; pharmacokinetics; radiometabolism; whole-body distribution J Nucl Med 2013; 54:867-872 DOI: 10.2967/jnumed.112.114082 Prost ate cancer (PCa) is the second most common cancer in men globally (1) and the most common cancer in developed countries (2). However, conventional imaging techniques such as ultrasound, contrast-enhanced CT, or MR imaging have limited sensitivity and specificity for detecting primary, metastatic, and recurrent PCa (3). PET/CT plays an important role in the attempt to improve and individualize therapeutic approaches in oncology. The most widely used tracer, 18 F-FDG, shows a high excretion in the urinary bladder and demonstrates generally an unsatisfactory uptake in PCa, especially in the early phase (4,5). Tracers that depict lipid metabolism such as 11 C-choline and 11 C-acetate have already been applied for imaging PCa, but they accumulate also in prostatic hyperplasia, with overlapping uptake in benign and malignant intraprostatic lesions (6-8). Consequently, there is an urgent need for more PCa-specific tracers.Gastrin-releasing peptide receptors (GRPr) are highly overexpressed in a variety of human tumors including PCa (9). Preclinical data suggest the possibility of a high PCa-specific signal with radiolabeled bombesin analogs targeting GRPr (10). These analogs could potentially provide better and more specific diagnosis than 18 F-FDG or tracers such as 11 C-choline or 11 C-acetate.68 Ga-DOTA-4-amino-1-carboxymethylpiperidine-D-PheGln-Trp-Ala-Val-Gly-His-Sta-Leu-NH 2 (BAY 86-7548; also known as RM2) is a bombesin antagonist with high GRPr affinity. The purpose of this first-in-human study was to investigate the safety, tolerability, metabolism, pharmacokinetics, biodistribution, and radiation dosimetry of BAY 86-7548 in healthy volunteers receiving an intravenous injection of this a...

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