Practices in prescribing protein substitutes for PKU in Europe: No uniformity of approach.

BACKGROUND: There appears little consensus concerning protein requirements in phenylketonuria (PKU). METHODS: A questionnaire completed by 63 European and Turkish IMD centres from 18 countries collected data on prescribed total protein intake (natural/intact protein and phenylalanine-free protein substitute [PS]) by age, administration frequency and method, monitoring, and type of protein substitute. Data were analysed by European region using descriptive statistics. RESULTS: The amount of total protein (from PS and natural/intact protein) varied according to the European region. Higher median amounts of total protein were prescribed in infants and children in Northern Europe (n=24 centres) (infants <1 year, >2-3g/kg/day; 1-3 years of age, >2-3 g/kg/day; 4-10 years of age, >1.5-2.5 g/kg/day) and Southern Europe (n=10 centres) (infants <1 year, 2.5 g/kg/day, 1-3 years of age, 2 g/kg/day; 4-10 years of age, 1.5-2 g/kg/day), than by Eastern Europe (n=4 centres) (infants <1 year, 2.5 g/kg/day, 1-3 years of age, >2-2.5 g/kg/day; 4-10 years of age, >1.5-2 g/kg/day) and with Western Europe (n=25 centres) giving the least (infants <1 year, >2-2.5 g/kg/day, 1-3 years of age, 1.5-2 g/kg/day; 4-10 years of age, 1-1.5 g/kg/day). Total protein prescription was similar in patients aged >10 years (1-1.5 g/kg/day) and maternal patients (1-1.5 g/kg/day). CONCLUSIONS: The amounts of total protein prescribed varied between European countries and appeared to be influenced by geographical region. In PKU, all gave higher than the recommended 2007 WHO/FAO/UNU safe levels of protein intake for the general population.

[Comparative study of special products "Tetraphen" and "Phenyl-free" in diet therapy of children with phenylketonuria]. / Sravnitel'naia otsenka ispol'zovaniia spetsializirovannykh produktov "Tetrafen" i "Fenil-fri" v dietoterapii detei, bol'nykh fenilketonuriei.

Basing on the comparative clinical and biochemical evaluation of the usage of the specialized product "Tetraphen" (Russia) and early utilized product "Phenyl-Free" (USA) it has been shown that "Tetraphen" does not yield to "Phenyl-Free", while some of its parameters (energy value, carbohydrate content) even in the higher degree correspond to the physiologic requirements of this aged children suffering from phenylketonuria. Intake of this product in smaller doses completely covers their requirements for the basic food ingredients. High frequency of carotenoids insufficiency in children received both "Tetraphen" and "Phenyl-Free" demonstrate necessity of the diet correction by means of beta-carotene additional supplementation.

[Structure-functional properties of conjugates of proteins with polyalkylene oxides: study by a fluorescence method]. / Strukturno-funktsional'nye svoistva kon''iugatov belkov s polialkilenoksidami: issledovanie metodom fluorestsentsii.

A fluorescent study of some structural and functional properties of conjugates of a number of proteins (bovine serum albumin, pyruvate kinase, alpha-chymotrypsin, and the two toxic proteins of plant origin--ricin and viscumin) with polyalkylene oxides (polyethylene glycol and pluronic) has been carried out. Analysis of the intrinsic protein fluorescence showed that the structure and stability of various protein conjugates to denaturing agents change only slightly: the conformational mobility of tryptophan residues accessible to the solvent decreases, whereas that of tryptophan residues localized in the protein regions of low polarity remains unchanged. Besides, the conjugates display a higher thermal stability in comparison with their native proteins. The fluorescence of 1-anilinonaphthalene-8-sulfonic acid and water insoluble 2',3',4',5'-tetrabenzoylriboflavin bound to the native and modified proteins indicated that modification of the proteins with polyalkylene oxides decreased the polarity and increased the viscosity of the microenvironment. Hence, this modification makes it possible to change some functional characteristics of the protein without causing any significant changes in its structure.

[Calcium homeostasis and calcium-regulating hormones in young children with phenylketonuria]. / Sostoianie kaltsievogo gomeostaza i kaltsiireguliruiushchikh gormonov u detei rannego vozrasta, bolnykh fenilketonuriei.

Calcium and calcium-regulating hormones were investigated in 19 infants with phenylketonuria. Parathyroid hormone, osteocalcin, dehydrocholecalciferol were found elevated while calcitonin reduced in the serum of the infants prior to the diet. Total calcium and phosphorus remained stable in the course of the study. Element diet resulted in reduced serum parathormone levels though surpassing those of healthy subjects. This fact is attributed to primary metabolic disorders responsible for the onset of hyperparathyroidism. The conclusion is made that element diet is unable to change calcium homeostasis and that of calcium-regulating hormones in infants with phenylketonuria.

[Features of the structure of catalytic subunits of toxins, inhibiting protein synthesis. I. The effect of pH and interaction with the B-chain of ricin]. / Osobennosti struktury kataliticheskikh sub''edinits toksinov, ingibiruiushchikh belkovyi sintez. I. Vliianie pH, vzaimodeistvie s B-tsep'iu ritsina.

A comparative study of gelonin and A-chains of ricin, mistletoe lectin I and diphtheria toxin was undertaken. The effect of pH was studied on: a) the conformation of the proteins under study using intrinsic fluorescence; b) interaction of these proteins with ricin B-chain using gel-filtration. Structural stability of the proteins was assessed according to denaturing action of guanidine hydrochloride and temperature, and localization of tryptophan residues was determined using fluorescence quenching by I-, Cs+ and acrylamide. All investigated proteins were shown to undergo the conformational changes when a environment became acidic. In comparison with an intact protein--gelonin, the A-chains of ricin, a mistletoe lectin and a diphtheria toxin are less stable. At pH less than 5.0 tryptophan residues became more accessible to quencher and a positive charge of the surrounding area increases (in the case of gelonin it is negatively charged). No reliable interaction of a ricin B-chain with both gelonin and A-chain of diphtheria toxin was observed. The interaction of a ricin B-chain with a A-chain of mistletoe lectin I is weaker than that with ricin A-chain and is practically pH-independent.

Immunotoxin with mistletoe lectin I A-chain and ricin A-chain directed against CD5 antigen of human T-lymphocytes; comparison of efficiency and specificity.

Monoclonal anti-CD5 antibody was coupled to the enzymatically active subunit of plant toxin [either mistletoe lectin I (ML) or ricin]. The obtained conjugates proved to be selectively toxic to CD5-bearing target cells. The immunotoxin prepared from ML A-chain (MLA) was as toxic as native ML and approximately 80-fold more active than the corresponding conjugate with ricin A-chain (RTA). The comparative studies of the structural properties of isolated MLA and RTA were carried out using intrinsic fluorescence spectroscopy. The results showed similar properties for both proteins. No antigenic cross-reactivity against both toxins was detected when using polyclonal antibodies. The results suggest that MLA-antibody conjugates may be potential candidates for therapeutical use.

[The structure of toxic protein, the mistletoe lectin, at different pH: the study using intrinsic fluorescence method]. / Struktura toksichnogo belka-lektina iz omely-pri razlichnykh pH: issledovanie metodom sobstvennoi fluorestsentsii.

The effects of pH on the conformation of mistletoe lectin I and its isolated A- and B-subunits has been investigated by using the methods of intrinsic fluorescence. By the denaturating action of guanidine hydrochloride and the influence of the quenchers (I-, Cs+, acrylamide) the structural stability of the native protein and its isolated subunits was estimated. Treatment of the protein with the denaturant and quenchers revealed its different structure at pH 7.0 and 4.0. At pH 4.0 tryptophan residues become more accessible to quenchers, positive charge of the surrounding area increases and the protein becomes more stable to the action of denaturant. The structure of the isolated A- and B-chains of mistletoe lectin I differs considerably from that of the whole protein: a) its stability to the action of guanidine hydrochloride is lower; b) it depends on the ionic strength of the solvent; c) it is characterized by increased accessibility of tryptophan residues to quenchers (for B-chain). Differences between the conformations of the isolated chains at pH 7.0 and 4.0 are marked more strongly; moreover, at pH 4.5 the B-chain undergoes structural transition. The possible relationship between structural peculiarities of mistletoe lectin I and the mechanism of its transmembrane transfer is discussed.

Similarity of protein conformation at low pH and high temperature observed for B-chains of two plant toxins: ricin and mistletoe lectin 1.

A comparative study of subunits of two plant toxins, ricin (RC) and mistletoe lectin 1 (ML 1), has been undertaken. The study suggests that isolated B-chains of these toxins undergo structural transitions at low pH (from 5 to 4) and high temperature (45 degrees C), and as a result of the guanidine hydrochloride denaturing effect (to 3 M). Our results indicate that the protein conformation observed at low pH and high temperature are similar, though not identical. These conformations differ from the native one (pH 7, 25 degrees C), the protein in these conformations has a low fluorescence tryptophan intensity, and tryptophans are more exposed to aqueous solutions. However, these conformations differ also from the state unfolded by guanidine hydrochloride. An assumption is made that the partially denatured protein structure, exhibited at low pH and high temperature, is a functionally essential intermediate state of the toxin B-chain.