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Biomedical subjects

R J FitzGerald

Publications and source records attributed to R J FitzGerald.

At least 19 recordsLinked to original sources
PubMed2006

Enzymatic debittering of food protein hydrolysates.

Protein hydrolysates have a range of applications in the food and allied healthcare sectors. Bitterness is a negative attribute associated with most food protein hydrolysates. The development of biotechnological solutions for hydrolysate debittering is ongoing. Specific enzymatic debittering strategies have focused on the application of proline specific exo- and endopeptidases given the contribution of proline residues to peptide/hydrolysate bitterness. Hydrolysate manufacturing conditions may also play an important role in bitterness development. Practical solutions to hydrolysate debittering are likely to involve judicious choice of enzymatic processing conditions in conjunction with the use of peptidase activities having targeted hydrolytic specificity.

Aminopeptidases↗
PubMed2004

Modification of the furanacryloyl-L-phenylalanylglycylglycine assay for determination of angiotensin-I-converting enzyme inhibitory activity.

Angiotensin-I-converting enzyme (ACE, EC 3.4.15.1) plays a central role in the regulation of blood pressure in man. The objective of this study was to evaluate and modify the furanacryloyl-L-phenylalanylglycylglycine (FAPGG) assay method for quantification of ACE activity. The fixed time conditions developed for assay of ACE activity were as follows: 0.8 mM FAPGG, 175 + or - 10 units l(-1) ACE, incubation at 37 degrees C for 30 min and enzyme inactivation with 100 mM ethylenediaminetetra-acetic acid (EDTA). Hydrolysis of FAPGG to FAP and GG was quantified by measuring the decrease in absorbance at 340 nm. It was shown that increasing the level ACE activity in the assay from 155 to 221 + or - 15 units l(-1) resulted in a corresponding increase in the apparent IC(50) value for Captopril from 9.10 to 39.40 nM. Similar trends in the apparent IC50 values for a whey protein hydrolysate were obtained. The results demonstrate the requirement for carefully controlling ACE activity levels in the assay in order to obtained comparable and reproducible values for the inhibitory potency of ACE inhibitors.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed2003

Detection of caseinophosphopeptides in the distal ileostomy fluid of human subjects.

Caseinophosphopeptides (CPP) were detected for the first time in ileostomy fluid, collected at 2 h intervals for 10 h post milk and CPP ingestion, from human volunteers with an ileostomy. The level of CPP present in ileostomy fluid obtained from milk-fed volunteers was markedly higher than that from volunteers fed with selected CPP preparations. The findings are based on HPLC analysis in combination with peptide-bound P determination, thin-layer electrophoresis and amino acid analysis, together with ELISA studies using polyclonal antibodies raised against a set of CPP to detect immunoreactive CPP in ileostomy fluid. These procedures allowed the detection of nm concentrations of CPP. CPP, which can be released during intestinal digestion, may function as bioactive constituents and carriers for different minerals, especially Ca, and may be used as ingredients in functional foods or pharmaceutical preparations.

Adult↗
PubMed2003

Biofunctional peptides from milk proteins: mineral binding and cytomodulatory effects.

The protein fraction of milk contains many valuable components and biologically active substances. Moreover, milk proteins are precursors of many different biologically active peptides which are inactive within the sequence of the precursor protein but can be released by enzymatic proteolysis. Many milk protein-derived peptides, such as caseinophosphopeptides, reveal multi-functional bioactivities. Caseinophosphopeptides can form soluble organophosphate salts and may function as carriers for different minerals, especially calcium. Furthermore, they have been shown to exert cytomodulatory effects. Cytomodulatory peptides inhibit cancer cell growth or they stimulate the activity of immunocompetent cells and neonatal intestinal cells, respectively. Several bioactive peptides derived from milk proteins are potential modulators of various regulatory processes in the body and thus may exert beneficial physiological effects. Caseinophosphopeptides are already produced on an industrial-scale and as a consequence these peptides have been considered for application as ingredients in both 'functional foods' and pharmaceutical preparations. Although the physiological significance as exogenous regulatory substances is not yet fully understood, both mineral binding and cytomodulatory peptides derived from bovine milk proteins are claimed to be health enhancing components that can be used to reduce the risk of disease or to enhance a certain physiological function.

Adjuvants, Immunologic↗
PubMed2000

Opioid peptides encrypted in intact milk protein sequences.

Opioid agonistic and antagonistic peptides which are inactive within the sequence of the precursor milk proteins can be released and thus activated by enzymatic proteolysis, for example during gastrointestinal digestion or during food processing. Activated opioid peptides are potential modulators of various regulatory processes in the body. Opioid peptides can interact with subepithelial opioid receptors or specific luminal binding sites in the intestinal tract. Furthermore, they may be absorbed and then reach endogenous opioid receptors.

Animal Nutritional Physiological Phenomena↗
PubMed2000

Milk protein-derived peptide inhibitors of angiotensin-I-converting enzyme.

Numerous casein and whey protein-derived angiotensin-I-converting enzyme (ACE) inhibitory peptides/hydrolysates have been identified. Clinical trials in hypertensive animals and humans show that these peptides/hydrolysates can bring about a significant reduction in hypertension. These peptides/hydrolysates may be classified as functional food ingredients and nutraceuticals due to their ability to provide health benefits i.e. as functional food ingredients in reducing the risk of developing a disease and as nutraceuticals in the prevention/treatment of disease.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1999

Catecholamines in urine after death.

Noradrenaline, adrenaline and dopamine levels were measured using high-performance liquid chromatography (HPLC) and electrochemical detection and related to urine creatinine in 30 specimens from unselected autopsies. Values calculated from patients with essential hypertension were used as a reference and raised values of noradrenaline, adrenaline and dopamine were found in 76.6, 80 and 23.3%, respectively. Using the Mann-Whitney U test, there was no difference between the 11 patients with myocardial infarction and the seven who died from severe head injury or multiple trauma. The median values in mmol/mol creatinine for patients with myocardial infarction and trauma were 0.07 and 0.12 for noradrenaline and 0.012 and 0.024 for adrenaline, respectively. Physiological stress is common before death and urine noradrenaline values at autopsy overlap those found in some normal subjects and at autopsy in patients with phaeochromocytoma.

Adolescent↗
PubMed1999

Hydrolysis of alphas1- and beta-casein-derived peptides with a broad specificity aminopeptidase and proline specific aminopeptidases from Lactococcus lactis subsp. cremoris AM2.

Aminopeptidase hydrolysis of alpha(s)1 - and beta-casein-derived synthetic peptides containing non-consecutive and consecutive proline residues was characterised. Aminopeptidase P (Pep P) (EC 3.4.11.9) or post-proline dipeptidyl aminopeptidase (PPDA) (EC 3.4.14.5) along with lysine-paranitroanilide hydrolase (KpNA-H) (EC 3.4.11.1) activities are required in the degradation of peptides containing non-consecutive proline residues. However, both Pep P and PPDA along with KpNA-H are required for hydrolysis of peptides containing consecutive proline residues. The results demonstrate the mechanism by which combinations of purified general and proline specific aminopeptidases from Lactococcus lactis subsp. cremoris AM2 hydrolyse peptides containing proline residues.

Aminopeptidases↗
PubMed1999

Lactokinins: whey protein-derived ACE inhibitory peptides.

Angiotensin-I-converting enzyme (ACE) has been classically associated with the renin-angiotensin system which regulates peripheral blood pressure. Peptides derived from the major whey proteins, i.e. alpha-lactalbumin (alpha-la) and beta-lactoglobulin (beta-lg) in addition to bovine serum albumin (BSA), inhibit ACE. Some of these inhibitory peptides, i.e. alpha-lactorphin (alpha-la f(50-53)), beta-lactorphin (beta-lg f(102-105)), beta-lactotensin (beta-lg f(146-149) and albutensin A (BSA f(208-216)), have other bioactivities. The most potent lactokinin reported to date, (beta-lg f(142-148)), has an ACE IC50 of 42.6 mumol/l. While they do not have the inhibitory potency of synthetic drugs commonly used in the treatment of hypertension, these naturally occurring peptides may represent nutraceutical/functional food ingredients for the prevention/treatment of high blood pressure. Studies with gastric and pancreatic proteinase digests of whey proteins indicate that enzyme specificity rather than extent of hydrolysis dictates the ACE inhibitory potency of whey hydrolysates.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1997

Identification of a novel angiotensin-I-converting enzyme inhibitory peptide corresponding to a tryptic fragment of bovine beta-lactoglobulin.

The angiotensin-I-converting enzyme (ACE) inhibitory activity of a tryptic digest of bovine beta-lactoglobulin (beta-lg) was investigated. Intact beta-lg essentially did not inhibit ACE while the tryptic digest gave an 84.3% inhibition of ACE. Peptide material eluting between 20 and 25% acetonitrile during C18 solid-phase extraction of the beta-lg tryptic digest inhibited ACE by 93.6%. This solid-phase extraction fraction was shown by mass spectroscopy to contain beta-lg f(142-148). This peptide had an ACE IC50 value of 42.6 micromol/l. The peptide was resistant to further digestion with pepsin and was hydrolysed to a very low extent with chymotrypsin. The contribution of specific amino acid residues within the peptide to ACE inhibitory activity and the potential application of this peptide as a nutraceutical is discussed.

Amino Acid Sequence↗
PubMed1996

Synthetic peptides corresponding to alpha-lactalbumin and beta-lactoglobulin sequences with angiotensin-I-converting enzyme inhibitory activity.

Novel angiotensin-I-converting enzyme (ACE) inhibitory activities were detected in synthetic peptides corresponding to sequences of beta-lactoglobulin and alpha-lactalbumin and which are known to possess opioid activity. Using hippuryl-histidyl-leucine as substrate, the tetrapeptides beta-lactorphin (Tyr-Leu-Leu-Phe), alpha-lactorphin (Tyr-Gly-Leu-Phe) and beta-lactotensin (His-Ile-Arg-Leu) were shown to have IC50 values of 171.8, 733.3 and 1153.2 microM, respectively. Related dipeptides also inhibited ACE, with Tyr-Leu being the most potent, having an IC50 value of 122.1 microM.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1995

The clinical and laboratory correlates of an increased urinary 5-hydroxyindoleacetic acid.

Over a five-and-a-half-year period, there were 298 laboratory requests for urinary 5-hydroxyindoleacetic acid (5-HIAA). The clinical and laboratory associations of the 24 patients in which there were 43 urinary 5-HIAA 24-h collection results greater than the laboratory upper reference limit are detailed. Four were confirmed carcinoid tumours and two were phaeochromocytomas. Flushing was a prominent symptom in 46% and diarrhoea or altered bowel habit in 37%. Associated with the raised urinary 5-HIAA values were increased levels of 4-hydroxy-3-methoxymandelic acid and homovanillic acid in 14.3% and 21%, respectively, of those collections where the metabolites were requested. Diagnostic imaging was performed in 57%. While the specificity was 88%, 5-HIAA is relatively insensitive in the diagnosis of carcinoid tumours and a more widespread use of diagnostic imaging including isotope scanning with labelled metaiodo-benzylguanidine, vasoactive intestinal peptide and octreotide is suggested.

Adolescent↗
PubMed1994

Interpretation of random urinary catecholamines and their metabolites in neuroblastoma.

This study reports experience in the estimation of urinary catecholamines (uCATs) and their metabolites in the diagnosis and follow-up of neuroblastoma. Random urine samples were assayed for dopamine, noradrenaline and adrenaline, together with their metabolites 4-hydroxy 3-methoxymandelic acid (HMMA) and homovanillic acid (HVA), using HPLC with electrochemical detection. Twenty of 21 patients had elevation of one or more uCATs metabolites at diagnosis. Patients were monitored serially from diagnosis and, in those patients who had delayed resection of primary tumour (n = 13), particular attention was paid to levels at the pre-surgical evaluation as an indicator of persistence of viable disease at the time of surgery; dopamine proved to be the most accurate indicator of persistent disease at this time. Five of these patients developed recurrent disease, 4 of whom had elevation of two or more uCATs metabolites at the time of relapse. Several conclusions can be drawn from this study: (a) results for HMMA, HVA and dopamine in random urine samples will detect all but the most biochemically immature or inert tumours; (b) dopamine may be the most reliable indicator of persistent disease and (c) noradrenaline and adrenaline measurements were of little benefit. As results are expressed in relation to urinary creatinine, excretion of which may be affected by dietary protein and is therefore not constant, borderline results should be repeated.

Catecholamines↗
PubMed1992

Intracellular pH and the role of D-lactate dehydrogenase in the production of metabolic end products by Leuconostoc lactis.

The kinetics of lactate dehydrogenase from Leuconostoc lactis NCW1 were studied. The pH optimum for the enzyme depended on the concentration of pyruvate used in the assay and the enzyme displayed an ordered mechanism with respect to substrate binding. The Km for pyruvate and NADH and the Vmax of the enzyme decreased 20-, 30- and 6-fold respectively as the pH decreased from 8.0 to 5.0. No activators were found and none of the intermediates of the phosphoketolase pathway tested inhibited the enzyme. ATP, ADP, GTP and NAD+ were inhibitory. The intracellular volume (Vol(in)) and intracellular pH (pH(in)) decreased as the extracellular pH (pH(ex)) decreased. Co-metabolism of citrate and glucose affected the Vol(in) but did not affect the pH(in), which decreased by 0.6 units per unit change in pH(ex); at pH 7.0, the pH(in) and pH(ex) were equal. The results suggest that pH(in) may play a role in determining the production of diacetyl and acetoin at low pH by Leuconostoc.

Adenosine Diphosphate↗
PubMed1992

Reference values for urinary HMMA, HVA, noradrenaline, adrenaline, and dopamine excretion in children using random urine samples and HPLC with electrochemical detection.

Random urine samples were collected from 305 children aged from birth to 14 years and the values of hydroxymethoxymandelic acid, homovanillic acid, noradrenaline, adrenaline, and dopamine were measured by high-performance liquid chromatography with electrochemical detection. The results were reported relative to the urinary creatinine concentration and the values declined progressively with increasing age for each analyte with the exception of adrenaline. The results for each age group were not normally distributed and all values except outliers were retained in determining the upper reference limits.

Adolescent↗
PubMedDate not supplied

Phaeochromocytoma--a laboratory experience.

Thirteen phaeochromocytomas were found over five and a half years from 2,834 patient requests for tumour screens. HMMA (VMA) was the usual screening test requested. Free catecholamines were reported when specifically requested by clinicians and where the HMMA level was > 40 mumol/24 hr. HMMA and urinary free catecholamines were estimated using HPLC with electrochemical detection in acidified 24 hr collections. Noradrenaline was elevated in all thirteen, nine had raised adrenaline and two had raised levels of all three catecholamines. Urinary free catecholamines are the most appropriate analyte package in our circumstances for the diagnosis of phaeochromocytoma. HMMA if used alone could lead to false negative diagnoses but it has a role in minimising false negatives where urinary catecholamine results are normal.

Adrenal Gland Neoplasms↗