Phosphorous metabolites in boar spermatozoa. Identification of AMP by multinuclear magnetic resonance

An introduction to biological nuclear magnetic resonance spectroscopy

Nuclear magnetic resonance (NMR) spectroscopy is one of the most powerful analytical techniques available to biology. This review is an introduction to the potential of this method and is aimed at readers who have little or no experience in acquiring or analyzing NMR spectra. We focus on spectroscopic applications of the magnetic resonance effect, rather than imaging ones, and explain how various aspects of the NMR phenomenon make it a versatile tool with which to address a number of biological problems. Using detailed examples, we discuss the use of (1) H NMR spectroscopy in mixture analysis and metabolomics, the use of (13) C NMR spectroscopy in tracking isotopomers and determining the flux through metabolic pathways ('fluxomics') and the use of (31) P NMR spectroscopy in monitoring ATP generation and intracellular pH homeotasis in vivo. Further examples demonstrate how NMR spectroscopy can be used to probe the physical environment of a cell by measuring diffusion and the tumbling rates of individual metabolites and how it can determine macromolecular structures by measuring the bonds and distances which separate individual atoms. We finish by outlining some of the key challenges which remain in NMR spectroscopy and we highlight how recent advances-such as increased magnet field strengths, cryogenic cooling, microprobes and hyperpolarisation-are opening new avenues for today's biological NMR spectroscopists.

Regulatory properties of 6-phosphofructokinase and control of glycolysis in boar spermatozoa

Glycolysis is crucial for sperm functions (motility and fertilization), but how this pathway is regulated in spermatozoa is not clear. This prompted to study the location and the regulatory properties of 6-phosphofructokinase (PFK, EC 2.7.1.11), the most important element for control of glycolytic flux. Unlike some other glycolytic enzymes, PFK showed no tight binding to sperm structures. It could readily be extracted from ejaculated boar spermatozoa by sonication and was then chromatographically purified. At physiological pH, the enzyme was allosterically inhibited by near-physiological concentrations of its co-substrate ATP, which induced co-operativity, i.e. reduced the affinity for the substrate fructose 6-phosphate. Inhibition by ATP was reinforced by citrate and H+. Above pH 8, PFK lost all its regulatory properties and showed maximum activity. However, in the physiological pH range, PFK activity was very sensitive to small changes in effectors. At near-physiological substrate concentrations, PFK activity requires activators (de-inhibitors) of which the combination of AMP and fructose 2,6-bisphosphate (F2,6P2) was most efficient as a result of synergistic effects. The kinetics of PFK suggest AMP, F2,6P2, H+, and citrate as allosteric effectors controlling PFK activity in boar spermatozoa. Using immunogold labeling, PFK was localized in the mid-piece and principal piece of the flagellum as well as in the acrosomal area at the top of the head and in the cytoplasmic droplets released from the mid-piece after ejaculation.

Mapping hypoxia-induced bioenergetic rearrangements and metabolic signaling by 18O-assisted 31P NMR and 1H NMR spectroscopy

Brief hypoxia or ischemia perturbs energy metabolism inducing paradoxically a stress-tolerant state, yet metabolic signals that trigger cytoprotection remain poorly understood. To evaluate bioenergetic rearrangements, control and hypoxic hearts were analyzed with 18O-assisted 31P NMR and 1H NMR spectroscopy. The 18O-induced isotope shift in the 31P NMR spectrum of CrP, betaADP and betaATP was used to quantify phosphotransfer fluxes through creatine kinase and adenylate kinase. This analysis was supplemented with determination of energetically relevant metabolites in the phosphomonoester (PME) region of 31P NMR spectra, and in both aromatic and aliphatic regions of 1H NMR spectra. In control conditions, creatine kinase was the major phosphotransfer pathway processing high-energy phosphoryls between sites of ATP consumption and ATP production. In hypoxia, creatine kinase flux was dramatically reduced with a compensatory increase in adenylate kinase flux, which supported heart energetics by regenerating and transferring beta- and gamma-phosphoryls of ATP. Activation of adenylate kinase led to a build-up of AMP, IMP and adenosine, molecules involved in cardioprotective signaling. 31P and 1H NMR spectral analysis further revealed NADH and H+ scavenging by alpha-glycerophosphate dehydrogenase (alphaGPDH) and lactate dehydrogenase contributing to maintained glycolysis under hypoxia. Hypoxia-induced accumulation of alpha-glycerophosphate and nucleoside 5'-monophosphates, through alphaGPDH and adenylate kinase reactions, respectively, was mapped within the increased PME signal in the 31P NMR spectrum. Thus, 18O-assisted 31P NMR combined with 1H NMR provide a powerful approach in capturing rearrangements in cardiac bioenergetics, and associated metabolic signaling that underlie the cardiac adaptive response to stress.

The use of phosphocreatine plus ADP as energy source for motility of membrane-deprived trout spermatozoa

Live trout spermatozoa initiate flagellar motility for a short period of time (30 s at 18 degrees C), during which their mean beat frequency (BF) decreases steadily from 60 to 20 Hz; motility then stops abruptly. When demembranated, the motility of axonemes lasts much longer, up to 20 min, with high beat frequency, provided that ATP (millimolar concentration) and cAMP (micromolar) are added. In the present paper, the motility of demembranated trout sperm was investigated in the absence of added ATP in various incubation conditions relative to other substrates. Without the addition of exogenous creatine kinase, the addition of phosphocreatine (PCr) and ADP shows the appearance of a progressive activation of all sperm models with BF increasing with time up to high values. Without the addition of cAMP, the BF increases to lower values but flagella propagated poorly coordinated waves for only a few min. Similar progressive activation is also observed when only ADP is added (without any previous in vivo activation) and BF increases up to moderate values. In this latter case, no activation occurs without addition of cAMP. The respective roles of creatine kinase and adenylate kinase in this process were investigated by addition of specific inhibitors such as fluorodinitrobenzene and P1,P5-di(adenosine-5')pentaphosphate in the above described conditions. We conclude from these observations that all the elements necessary for a coupling between ADP/PCr/creatine kinase on one hand and ATP/ADP/dynein on the other appear to be present in trout spermatozoa: thus the existence of a shuttle sustaining this coupling is strongly suggested.

1H-NMR and (31)P-NMR analysis of energy metabolism of quiescent and motile turbot (Psetta maxima) spermatozoa

31P-NMR and (1)H-NMR were used to monitor changes of several compounds with high-energy bonds and metabolites prior to and after the initiation of motility of turbot spermatozoa (Psetta maxima). The obtained (31)P-NMR spectra revealed the presence of phosphomonoesters, phosphodiester, intracellular inorganic phosphate (Pi), phosphocreatine (PCr), and free nucleotide triphosphate. Following the activation of motility, the di- and tri-phosphate nucleotides, PCr, phosphomonoesters levels dropped while Pi levels increased. A significant increase of lactate was also seen at the end of the swimming phase. The compositions of seminal fluid and urine were also determined. Lipoproteins, formic acid, amino acid, and citric acid were detected in seminal fluid. Dimethyl amine, trimethylamine, and trimethylamine oxyde were found in urine. These data suggest that at least a part of the energy required during the swimming phase results from anaerobic fermentation and oxidative phosphorylation. J. Exp. Zool. 286:513-522, 2000.

Assignment of overlapping (1)H NMR signals in carp seminal plasma by proton-detected 2D C,H correlation spectroscopy

The (1)H NMR spectrum of the perchloric acid extract of carp seminal plasma was heavily congested. It is demonstrated that proton-detected C,H chemical shift correlation spectroscopy (HSQC, HSQC-TOCSY) allows an unequivocal identification of proline, glutamate, taurine, and methionine sulfoxide, although several key proton signals were strongly overlapped.

Identification of low-molecular-weight compounds in goat epididymis using multinuclear nuclear magnetic resonance

Multinuclear nuclear magnetic resonance (NMR) (1H, 13C, and 31P) studies have been performed on aqueous solutions of lyophilysates of cell-free extract, epididymal fluid, and intact cells from caput and cauda regions of epididymis of sacrificed goats. Identification of low-molecular-weight compounds present in different maturation phases of spermatozoa has been carried out. Several low-molecular-weight compounds have been identified by assigning 600 MHz 1H NMR spectra with the help of two-dimensional homonuclear and heteronuclear correlation spectroscopy such as double quantum filtered correlation spectroscopy and heteronuclear single quantum correlation spectroscopy. Homonuclear coupling constants have also been used to get unambiguous assignments of resonances. NMR data were compared with those of standard samples measured at same pH and with those reported in the literature. Identification of several amino acids, carbohydrates, and lipids have been made and their presence has been discussed in relation to their relevance to sperm functions. The presence of beta-alanine and hypotaurine has been reported for the first time in goat epididymis.