Pyrimidine nucleotidases/phosphotransferases from human erythrocyte

Two cytoplasmic pyrimidine 5'-nucleotidase have been purified from human erythrocytes to homogeneity and partially characterized. The two enzymes, indicated as PN-I and PN-II, preferentially hydrolyse pyrimidine 5'-monophosphates and 3'-monophosphates, respectively. The kinetic analysis demonstrate that pyrimidine 5'-nucleotidases, in the presence of suitable nucleoside substrates, can operate as phosphotransferases by transferring phosphate to various nucleoside acceptors, including nucleoside analogues known as important drugs widely used in chemotherapy.

Identification of the archaeal NMN adenylytransferase gene

Increasing evidence on the importance of fluctuations in NAD+ levels in the living cell is accumulating. Therefore a deeper knowledge on the regulation of coenzyme synthesis and recycling is required. In this context the study of NMN adenylyltransferase (EC 2.7.7.1),. a key enzyme in the NAD+ biosynthetic pathway, assumes a remarkable relevance. We have previously purified to homogeneity and characterized the protein from the thermophilic archaeon Sulfolobus solfataricus. The determination of partial sequence of the S. solfataricus enzyme, together with the recent availability of the genome sequence of the archaeon Methanococcus jannaschii, allowed us, based on sequence similarity, to identify the M. jannaschii NMN adenylyltransferase gene. As far as we know from literature, this is the first report on the NMN adenylyltransferase gene.

Synechocystis sp. slr0787 protein is a novel bifunctional enzyme endowed with both nicotinamide mononucleotide adenylyltransferase and 'Nudix' hydrolase activities

Synechocystis sp. slr0787 open reading frame encodes a 339 residue polypeptide with a predicted molecular mass of 38.5 kDa. Its deduced amino acid sequence shows extensive homology with known separate sequences of proteins from the thermophilic archaeon Methanococcus jannaschii. The N-terminal domain is highly homologous to the archaeal NMN adenylyltransferase, which catalyzes NAD synthesis from NMN and ATP. The C-terminal domain shares homology with the archaeal ADP-ribose pyrophosphatase, a member of the 'Nudix' hydrolase family. The slr0787 gene has been cloned into a T7-based vector for expression in Escherichia coli cells. The recombinant protein has been purified to homogeneity and demonstrated to possess both NMN adenylyltransferase and ADP-ribose pyrophosphatase activities. Both activities have been characterized and compared to their archaeal counterparts.

Variation of anatomic valve area during ejection in patients with valvular aortic stenosis evaluated by two-dimensional echocardiographic planimetry: comparison with traditional Doppler data

OBJECTIVES

Flow variations can affect valve-area calculation in aortic stenosis and lead to inaccuracies in the evaluation of the stenosis. Knowing that transvalvular flow varies normally within one beat, we designed this study to assess the response of the valve to intrabeat variation of flow during systole. Results were compared with flow-derived measurements.

BACKGROUND

Technological improvements now allow us to evaluate aortic valve area directly by short axis planimetry. This offers the possibility to perform serial planimetries during one ejection phase and analyze the intrabeat dynamic behavior of the stenotic-aortic valve and compare these measurements with flow-derived measurements.

METHODS

Forty echocardiograms displaying different degrees of aortic stenosis were analyzed by frame-by-frame planimetry of the valve area from onset of opening to complete closure. Maximal-mean area, opening and closing rates and ejection times were obtained and compared with Doppler-derived data.

RESULTS

Valve area varied during ejection. Stenotic valves opened and closed more slowly than normals and remained maximally open for a shorter period. Mean area by Doppler data corresponded more closely to maximal than to mean-planimetered area. Duration of flow was shorter than valve opening in severely stenotic valves. Discrepancies between Doppler-derived and two-dimensional (2D) measurements decreased in less stenotic valves.

CONCLUSIONS

Our observations reveal striking differences between the dynamics of normal and stenotic valves. Surprisingly, Doppler-derived mean-valve area correlated better with maximal-anatomic area than with mean-anatomic area in patients with aortic stenosis. Discrepancies between duration of flow and valve opening could explain this phenomenon.

Role of the central endogenous opiate system in patients with syndrome X

BACKGROUND

To evaluate the role of the endogenous opioid system (EOS) in abnormal pain perception in patients with syndrome X, we used a neuroendocrine approach, evaluating plasmatic luteinizing hormone (LH) changes after naloxone, a competitive antagonist of opioid receptors able to unblock tonic EOS inhibition on gonadotropin release. Thus LH response to naloxone test indicates the central EOS activity on hypothalamic luteinizing hormone-releasing hormone (LH-RH) inhibitory opioid receptors.

METHODS

Ten patients with syndrome X, 10 age-matched male patients with coronary artery disease (CAD), and 10 normal subjects were analyzed. Naloxone tests were performed between 8 and 9 am. Basal beta-endorphin and LH levels were determined on 4 blood samples at 20-minute intervals; after naloxone (0.1 mg/kg intravenously in 4 minutes), LH was measured on 8 samples at 15-minute intervals. In all patients the test was also performed after LH-RH administration. Anginal pain on exercise testing was subjectively scored on a 1 to 10 analogic scale and wall motion abnormalities were quantified by a wall motion score index.

RESULTS

Significant differences were found in LH release after naloxone (CAD 260.3 +/- 42.6 vs syndrome X 151.6 +/- 48.5 mIU/mL, P <.05), angina score (CAD 5.5 +/- 1.3 vs syndrome X 7.2 +/- 1.7, P <.05), and wall motion abnormalities (CAD 3.6 +/- 1. 2 vs syndrome X 2.8 +/- 1.9, P <.05).

CONCLUSIONS

The reduced LH release after naloxone in syndrome X, with a normal LH-RH response, suggests a lower central EOS activity, which may be related to the higher anginal pain perception.

New modalities of regional and global left ventricular function analysis: state of the art

Study of left ventricular (LV) regional and global function represents a main point of the cardiologic evaluation. This article presents an overview of the state of the art in quantitative analysis of ventricular wall motion and describes the different techniques available in clinical settings; we also present the personal experience of the authors in comparing conventional 2-dimensional (2D) echocardiography with other recently developed, more sophisticated techniques. Conventional 2D echocardiography mainly depends on the operator's ability. Moreover, the physiologic regional pattern of myocardial wall motion in different segments of left ventricle is still not completely known as well as the heart's rotational and translational movements. Qualitative and quantitative transesophageal echocardiography allows a better and more accurate evaluation of regional wall motion, and improves the on-line border detection feasibility even in patients with poor transthoracic echocardiographic window. The automated system for on-line endocardial border detection, color kinesis, and the power Doppler are, at the moment, promising techniques. Using magnetic resonance imaging as a "gold standard" for the study of global and regional left ventricular function, the investigators describe personal experiences with tissue Doppler imaging and a new computerized system for tissue Doppler images postprocessing analysis.

Three-dimensional echocardiographic assessment of the extension of dysfunctional mass in patients with coronary artery disease

Two-dimensional (2D) echocardiographic estimation of infarcted mass is limited by having only a few selected nonparallel views for data analysis. Volume-rendered three-dimensional (3D) echocardiography may be able to overcome the above limitations, because it uses multiple, parallel 2D images to derive quantitative data. Previous experimental studies demonstrated that 3D echocardiography is an accurate and reproducible method to assess dysfunctional mass. To estimate the accuracy of 3D echocardiography in humans, we evaluated 10 patients who had a single myocardial infarction. All patients underwent 2D and 3D echocardiography using the transesophageal approach, and contrast (gadolinium) magnetic resonance imaging (MRI), considered a reference standard for infarcted tissue detection. The mean extent of dysfunctional mass by MRI was 28 +/- 13 g and by 3D echocardiography was 30 +/- 12 g; the mean difference was 1.9 +/- 2.3 g (p = not significant). Linear regression analysis between the 2 measurements was y = 0.97x - 1.12, r = 0.98. Dysfunctional mass derived from 3D echocardiography reflects the real site and extension of damaged myocardium.

Suicidality in chronic abdominal pain: an analysis of the Hispanic Health and Nutrition Examination Survey (HHANES)

The objective of this study was to explore the relationship between suicidal ideation, suicidal attempts, depression and chronic abdominal pain in data gathered during a systematic epidemiologic survey, the Hispanic Health and Nutrition Examination Survey of the United States National Centre for Health Statistics. The material comprises data collected between 1982 and 1984 in samples of Hispanic groups in the United States. A sub-sample which initially comprised 5498 subjects had provided answers to questions concerning the thoughts about death, wishes to die, thoughts of committing suicide and suicide attempts, as well as information about complaints of chronic abdominal pain and responses to the Centre for Epidemiologic Studies Depression Scale (CES-D). Complete answers were available from 4964 subjects. The data were analyzed by tabulation, and logistic regression analyses. The lifetime prevalence of suicidality was much increased in subjects with pain compared with those without chronic abdominal pain. Rates for thoughts about death, wishing to die, suicidal ideation and suicide attempts were 2- to 3-times more frequent in those with chronic abdominal pain compared with those without. Logistic regression analyses and the calculation of odds ratios confirmed that the most powerful predictive factors for suicidality were first, the presence of significant depressive ideation, and second, the presence of chronic abdominal pain. There is a strong relationship between chronic abdominal pain and suicidality in the Hispanic population in the United States. This was particularly evident in the Puerto Rican population of the United States where both rates were much increased compared with other Hispanic citizens. The present data are new, but no conclusion can be drawn concerning causality because they are cross-sectional. They indicate the importance of the link between chronic abdominal pain and depression in this population.

Pyrimidine nucleotidases from human erythrocyte possess phosphotransferase activities specific for pyrimidine nucleotides

Two cytoplasmic forms of pyrimidine nucleotidase (PN-I and PN-II) have been purified from human erythrocytes to apparent homogeneity and partially characterized. They preferentially hydrolyse pyrimidine 5'-monophosphates and 3'-monophosphates respectively. PN-I and PN-II operate as interconverting activities, capable of transferring the phosphate from the pyrimidine nucleoside monophosphate donor(s) to various nucleoside acceptors, including important drugs like 3'-azido-3'-deoxy-thymidine (AZT), cytosine-beta-D-arabinofuranoside (AraC) and 5-fluoro-2'-deoxy-uridine (5FdUrd), pyrimidine analogues widely used in chemotherapy. Kinetic analysis showed linear behaviour for both PN-I and PN-II. PN-I phosphotransferase activity revealed higher affinity for oxynucleosides with respect to deoxy-nucleosides, whereas the contrary seems to be true for PN-II. These results show for the first time that soluble pyrimidine nucleotidases are endowed with pyrimidine-specific phosphotransferase activity.

Characterization of nicotinamide mononucleotide adenylyltransferase from thermophilic archaea

The enzyme nicotinamide mononucleotide (NMN) adenylyltransferase (EC 2.7.7.1) catalyzes the synthesis of NAD+ and nicotinic acid adenine dinucleotide. It has been purified to homogeneity from cellular extracts of the thermophilic archaeon Sulfolobus solfataricus. Through a database search, a highly significant match was found between its N-terminal sequence and a hypothetical protein coded by the thermophilic archaeon Methanococcus jannaschii MJ0541 open reading frame (GenBank accession no. U67503). The MJ0541 gene was isolated, cloned into a T7-based vector, and expressed in Escherichia coli cells, yielding a high level of thermophilic NMN adenylyltransferase activity. The expressed protein was purified to homogeneity by a single-step chromatographic procedure. Both the subunit molecular mass and the N-terminal sequence of the pure recombinant protein were as expected from the deduced amino acid sequence of the MJ0541 open reading frame-encoded protein. Molecular and kinetic properties of the enzymes from both archaea are reported and compared with those already known for the mesophilic eukaryotic NMN adenylyltransferase.

Role of transthoracic and transesophageal echocardiography in predicting embolic events in patients with active infective endocarditis involving native cardiac valves

Some studies describe an increased risk for emboli in infective endocarditis patients with large (>10 mm) and mobile vegetations. Other studies fail to demonstrate the above relation. Most studies have been performed using transthoracic echocardiography or with a monoplane transesophageal approach. The present study examines whether distinctive characteristics of vegetative lesions detected by transthoracic and multiplane transesophageal echocardiography are predictive of embolic risk. We reviewed both transthoracic and transesophageal echocardiograms of 57 patients with diagnosis of acute infective endocarditis and no documented or suspected previous embolic events. We evaluated site, length, width, mobility, and echodensity of vegetations. Twenty-five patients (44%) had embolic events. No statistical differences in age, sex distribution, location of endocarditis, or offending pathogens between embolic (n = 25) and nonembolic (n = 32) patients were found. There were no differences in any of the echo characteristics of vegetations detected by transthoracic and transesophageal approach in embolic and nonembolic groups. Thus, transthoracic and transesophageal characteristics of vegetations are not helpful in defining embolic risk in patients with infective endocarditis.

Valvular perforation in left-sided infective endocarditis: a prospective echocardiographic evaluation and clinical outcome

We undertook this study to determine the use of transthoracic and transesophageal echocardiography in detecting valvular perforation and the clinical impact of the latter on the outcome of left-sided infective endocarditis. Transthoracic echocardiography was performed in 58 consecutive patients with infective endocarditis. According to the study protocol, a subgroup of 42 patients also underwent transesophageal echocardiogrophy. At referral, 20 (34%) of 58 patients had echocardiographic evidence of valvular perforation (group A). No valvular perforations were found in the remaining 38 patients (group B). During a follow-up period of 27 +/- 16 months, a major complication occurred in 18 of 20 patients in group A and in 11 of 38 patients in group B (p < 0.0001). Univariate analysis indicated previous infective endocarditis, aortic involvement, and New York Heart Association functional class had a predictive value for valvular perforation (p < 0.001). Stepwise regression analysis confirmed aortic valve perforation as the only independent predictive variable for surgery and death. Valvular perforation is a common complication of infective endocarditis and is associated with an adverse outcome. Transthoracic echocardiography can detect or suggest valvular perforation in infective endocarditis, but transesophageal echocardiography better defines this complication and predicts severe heart failure or the need for early surgical management.

Two- and three-dimensional transesophageal echocardiography in patient selection and assessment of atrial septal defect closure by the new DAS-Angel Wings device: initial clinical experience

BACKGROUND

Transcatheter closure of atrial septal defects (ASDs) has been feasible and successful. Two-dimensional echocardiography (2DE) was applied to patients before selection and during device deployment. Three-dimensional echocardiography (3DE) can provide unique anatomic perspectives that might aid in improving device closure of ASDs.

METHODS AND RESULTS

Twenty-two consecutive patients were enrolled in an initial protocol for ASD device closure by the new DAS-Angel Wings occluder device. On the basis of transesophageal (TEE) 2DE and 3DE, 13 patients were considered eligible for device closure (9 secundum ASDs and 4 with patent foramen ovale associated with a cerebral vascular accident). Maximal ASD diameter and surrounding rim tissues were compared by TEE 2DE and 3DE and with balloon sizing measurements at catheterization. ASD size measured by TEE 2DE and 3DE correlated well (y = 1.0x + 0.049, r = .95), with good limits of agreement. However, balloon-stretched diameter measurements were systematically larger than echocardiographic measurements. Rim tissue measurements correlated well; however, TEE 3DE could demonstrate the entire shape and perimeter of the defect. Two-dimensional imaging provided reliable information during device deployment and for closure of small ASDs. However, 3DE was superior for imaging the device, especially when abnormally placed.

CONCLUSIONS

Three-dimensional imaging provides unique images and projections that were essential for understanding the spatial relationship of the device to the atrial septum. Three-dimensional echocardiography significantly enhanced our understanding of two-dimensional images and provided an imaging conceptualization that should aid in future development of device closures.

Three-dimensional echocardiographic estimation of infarct mass based on quantification of dysfunctional left ventricular mass

BACKGROUND

Two-dimensional echocardiography is useful for estimating the extent of infarct-related wall motion abnormalities. Such estimation, however, is based on a few selected views and extrapolated for the whole left ventricle (LV). This approach does not provide us with the actual amount of dysfunctional myocardium. Volume-rendered three-dimensional echocardiography (3DE) might overcome these limitations. In this study we explored (1) how well volume-rendered 3DE delineates regional dysfunction of the infarcted LV and (2) how well dysfunctional myocardial mass quantified by 3DE reflects the actual anatomic infarct mass.

METHODS AND RESULTS

3DE was performed before and 3 hours after coronary occlusion in 16 dogs. With the LV viewed in equidistant short-axis slices, the region of dysfunction was demarcated, and the dysfunctional myocardial mass was derived from this. With triphenyltetrazolium chloride staining, anatomic infarct regions were delineated, dissected, and weighed. The anatomic infarct mass was 16.3+/-7.7 g (mean+/-SD) (range, 6.4 to 31.4 g); the dysfunctional mass estimated by 3DE was 17.4+/-9.1 g (range, 5.2 to 39.0 g). The mean difference was 1.0 g. The correlation between dysfunctional mass (y) and infarct mass (x) was y=l.lx-0.6, r=.93 (P<.0001). The percentage of LV involved in infarction was 18.2+/-5.8% (range, 9.1% to 26.1%); the percentage of LV involved in regional dysfunction was 18.3+/-6.9% (range, 7.9% to 31.2%). The mean difference was 0.1%. The correlation between percentage of LV involved in infarction (x) and percentage of LV involved in dysfunction (y) was y=1.0x-1.1, r=.92 (P<.0001).

CONCLUSIONS

Volume-rendered 3DE crisply displays regional dysfunction of infarcted LV. 3DE-measured dysfunctional mass accurately reflects the anatomic infarct mass.

Effects of angiotensin-converting enzyme inhibition on left ventricular geometric patterns in patients with essential hypertension

Although angiotensin-converting enzyme inhibitors have been shown to affect left ventricular (LV) remodeling favorably in several conditions, it remains unclear whether they can influence LV geometric pattern in hypertension. To address this issue, 122 patients (71 men and 51 women; mean age = 51 +/- 10 years) with mild to moderate hypertension were studied prospectively. All underwent clinical evaluation and Doppler echocardiography at entry and more than 2 years of quinapril therapy (10-40 mg/day). According to either LV mass (normal if < 131 g/m2 for men or < 100 g/m2 for women) or the ratio of LV posterior wall thickness to diastolic diameter (RWT; normal if < 0.45) at baseline, 58 patients had normal mass and RWT, 18 patients had concentric remodelling (i.e., normal mass but increased RWT), 24 patients had eccentric hypertrophy (i.e., increased mass but normal RWT), and 22 patients had concentric hypertrophy (i.e., increase in both mass and RWT). After 6 months of quinapril therapy, all patients with normal left ventricles showed the maintenance of mass and RWT within normal limits. Patients with concentric remodeling showed no increase in mass but had a significant decrease in RWT. Patients with eccentric hypertrophy exhibited a significant reduction in mass with no substantial change in RWT. Patients with concentric hypertrophy had a significant reduction in both mass and RWT. Changes in LV mass and geometry were maintained during the 2-year period of treatment and were paralleled by improvements in Doppler indices of LV diastolic function in each group. It is concluded that quinapril, with its well-known effects on LV hypertrophy, modifies the LV geometric pattern of hypertensive patients favorably, regardless of the presence of an abnormal LV mass or RWT.

Malignant cardiac involvement in a family with myotonic dystrophy

BACKGROUND

In patients with myotonic dystrophy, histopathological and electrophysiologic abnormalities of cardiac conduction system may lead to sudden cardiac death due to atrioventricular block or to ventricular electrical instability.

METHODS

Four members of a family affected by myotonic dystrophy are reported, which underwent a cardiological examination including invasive electrophysiological study and prolonged follow-up. Other 3 members of the same family had died suddenly. No clinical data are available for 2 of these patients, while paroxysmal atrial flutter and non sustained ventricular tachycardia had been detected at Holter in the third one.

RESULTS

Signs of atrioventricular conduction impairment, poorly predictable with non invasive electrocardiography, were found in the 4 patients undergoing intracardiac electrophysiologic study. In 2/4 patients, both having dizzy spells and the most impaired atrioventricular conduction, a pace-maker was implanted. Polymorphic, non sustained ventricular response was induced in 2/4 patients, 1 of them with spontaneous high grade ventricular arrhythmias.

CONCLUSIONS

The respective role of atrioventricular conduction impairment and ventricular vulnerability in determining sudden death has not been stated so far in these patients. The observed polymorphic non sustained response should not be "a priori" disregarded as aspecific, since it could be the electrophysiological counterpart of a peculiar anatomic arrhythmogenic substrate. A comprehensive study, including invasive electrophysiology, is advisable in all patients with myotonic dystrophy whenever a member of their family presents with cardiac involvement, to assess the most probable life-threatening arrhythmogenic mechanism.

Volume-rendered, three-dimensional echocardiographic determination of the size, shape, and position of atrial septal defects: validation in an in vitro model

Accurate evaluation of atrial septal defect (ASD) size and shape is very important for the selection of patients for transcatheter occlusion. The ability of volume-rendered, three-dimensional echocardiography (3DE) in displaying ASDs in a dynamic mode has been demonstrated; however, its accuracy in sizing ASDs is unknown. To assess this, we performed 3DE of 10 explanted pig hearts in which ASDs of various locations, sizes, and shapes had been experimentally created. From en face 3DE views of the atrial septum containing the defects, major and minor diameters of the defect were measured by a blinded observer, and these data were compared to direct anatomic measurements. The correlations between 3DE and anatomy for the major and minor ASD diameters were y = 0.83x + 3.4 (r = 0.97, p < 0.0001) and y = 0.92x + 1.3 (r = 0.92, p < 0.0001) respectively. The correlation between the measures for major and minor axis ratio was y = 1.06 x - 0.052, r = 0.91, p < 0.0002. Good agreement between both methods of measurements was demonstrated for all measurements. In addition, 3DE portrayed the location and shape of the defects accurately. Thus 3DE provides excellent visualization of ASD and is able to accurately define the size of the defects. These qualitative and quantitative capabilities enhance the clinical potential of this technique in the appraisal of ASDs for decisions regarding application of closure devices.

Three-minute high-performance liquid chromatographic assay for NMN adenylyltransferase using a 20-mm-long reversed-phase column

NMN adenylyltransferase (NAD pyrophosphorylase; NMNAT) reversibly catalyzes the synthesis of NAD from ATP and NMN. In this paper, we describe a rapid and sensitive high-performance liquid chromatographic assay for NMNAT, which uses a 20-mm-long C18 reversed-phase (RP) column. The activity was measured by separating in less than 3 min the substrates (NMN and ATP) from the product (NAD) with 0.1 M potassium phosphate, pH 6.0, at a 2 ml/min flow-rate and 22 degrees C. NAD was directly quantitated from its ultraviolet absorbance. Amounts of NAD as small as 25 pmol could be measured. The activity value closely agreed with that determined by the spectrophotometric assay. This method was successfully applied to the determination of NMNAT activity in human placental and bull testis extracts, as well as in rat pheochromocytoma (PC12) cells.

Effectiveness of venlafaxine in patients hospitalized for major depression and melancholia

BACKGROUND

This study was undertaken to compare the antidepressant efficacy and short-term safety of venlafaxine with those of placebo in hospitalized patients with major depression and melancholia.

METHOD

Ninety-three inpatients with a minimum prestudy Montgomery-Asberg Depression Rating Scale (MADRS) score of 25 were treated for up to 4 weeks with either venlafaxine or placebo. Dosage averaged approximately 350 mg/day during Weeks 2 to 4. Efficacy and safety were assessed throughout the study. Efficacy was evaluated using the MADRS, the 21-item Hamilton Rating Scale for Depression (HAM-D), and the Clinical Global Impressions (CGI) scale. Recorded study events, vital signs and body weight measurements, laboratory determinations, physical examinations, and ECG recordings were used to assess safety.

RESULTS

Venlafaxine provided significantly greater improvement in the MADRS scores after 4 days and in the HAM-D scores after 1 week than did placebo. Response rate (based on a 50% decrease in MADRS scores) was 65% (30 of 46 patients) for venlafaxine and 28% (13 of 47 patients) for placebo. Significantly more placebo-treated patients (40%; N = 19) than venlafaxine-treated patients (9%; N = 4) discontinued treatment early because of lack of efficacy. Nausea and sweating were the most common events, occurring at a significantly higher rate in the venlafaxine group.

CONCLUSION

Venlafaxine is an effective and well-tolerated antidepressant in hospitalized patients with major depression and melancholia.

NMN adenylyltransferase from bull testis: purification and properties

The purification procedure of NMN adenylyltransferase from bull testis presented here consists of a heat step and an acidic precipitation followed by four chromatographic steps, including dye ligand, adsorption and hydrophobic chromatography. The final enzyme preparation subjected to non-denaturing and denaturating PAGE with silver nitrate staining exhibited a single band. At this step the enzyme appeared to be homogeneous. The M(r) value of the native enzyme calculated by gel filtration was about 133,000. The protein appeared to possess a quaternary structure with four subunits of apparent M(r) 33,000 without disulphide interchain bonds. Isoelectric experiments gave a pI of 6.2, and pH studies showed the possible presence of an acidic group in the active site having a pKa of 4.9. Analysis of the amino acid composition showed the presence of more acidic residues than basic ones, according to the pI value calculated by Mono P FPLC. The Ea calculated by Arrhenius plot gave an apparent value of 55.7 kJ/mol. The Km values for NMN, ATP, NAD+ and PPi were 0.11, 0.023, 0.37 and 0.16 nM respectively. The polyclonal antiserum produced against the NMN adenylyltransferase reacted with the purified enzyme at different dilutions and recognized the enzyme in the homogenate as well.