Peptides amino acid uptake

Field studies point in a similar direction field comparisons of peptide hydrolysis rates and amino acid turnover in coastal sediments showed that amino acid production could exceed uptake by a factor of approximately 8 (Pantoja and Lee, 1999). A comparison of potential enzyme activities and sedimentary amino acid and carbohydrate inventories in sediments from the Ross Sea also showed that potential hydrolysis rates on time scales of hours should in theory rapidly deplete sedimentary amino acid and carbohydrate inventories (Fabiano and Danovaro, 1998). In deep-sea sediments, Poremba (1995) also found that potential enzyme activities in theory could exceed total sedimentary carbon input by a factor of 200. Finally, Smith et al. s (1992) investigation of potential hydrolysis rates and amino acid uptake in marine snow demonstrated that the particle-associated bacteria were potentially producing amino acids far in excess of their own carbon demand. 

The reason for this may be that there is now evidence to show that the corpora cardiaca (CC) secretes a peptide (12) which stimulates amino acid uptake by the gland. Furthermore, many attempts to demonstrate that JH is present in the pregnant tsetse have so far failed. Activity of the large sexual accessory gland of alla-tectomized Perlplaneta amerlcana is also inhibited iu vivo by 20-OHE 03). 

This phenomenon may be explained if one considers that a great deal of the amino acids are taken up in the form of peptides rather than by a process of essentially complete hydrolysis to free amino acids in the gut lumen. Evidence from many laboratories including those of Matthews (30) and Adibi (31) has shown that perhaps more than 50% of amino acid uptake can be accounted for by transport of intact peptides. There appears to be specificity for some portion of the peptide, but at this time it is not clear how large the recognition sequence must be... 

Cobalt(ll) forms many complexes which can exhibit oxygen-carrying properties (2,19). Reversible oxygen uptake in solutions of cobalt (ll)-histidine (33-36), and cobalt (II) in the presence of a-amino acids and peptides (37—39) has been known for some time. The reaction of cobalt (II) with dipeptide was first observed in enzymic studies involving glycyl-glycine (40). 

In this work we will focus on the use of the cubic phase as a delivery system for oligopeptides - Desmopressin, Lysine Vasopressin, Somatostatin and the Renin inhibitor H214/03. The amino acid sequences of these peptides are given in Table I. The work focuses on the cubic phase as a subcutaneous or intramuscular depot for extended release of peptide drugs, and as a vehicle for peptide uptake in the Gl-tract. Several examples of how the peptide drugs interact with this lipid-water system will be given in terms of phase behaviour, peptide self-diffusion, in vitro and in vivo release kinetics, and the ability of the cubic phase to protect peptides from enzymatic degradation in vitro. Part of this work has been described elsewhere (4-6). 

The amino acid, activated by uptake of SO3, reacts with a second molecule of amino acid to form the dipeptide, which can in turn react further to form a tripeptide (and so on). This peptide synthesis model, which is supported by experimental evidence, appeals because of its simplicity it may well correspond much more closely to conditions on the primeval Earth than do some other models (Chen and Yang, 2007). 

Han, H.-K., D.-M. Oh, and G. L. Amidon. Cellular uptake mechanism of amino acid ester prodrugs in Caco-2/hPEPTl cells overexpressing a human peptide transporter. Pharm. 

Simply on the basis of the normal composition of marine organisms, we would expect proteins and peptides to be normal constituents of the dissolved organic carbon in seawater. While free amino acids might be expected as products of enzymic hydrolysis of proteins, the rapid uptake of these compounds by bacteria would lead us to expect that free amino acids would normally constitute a minor part of the dissolved organic pool. This is precisely what we do find the concentration of free amino acids seldom exceeds 150 xg/l in the open ocean. It would be expected that the concentration of combined amino acids would be many times as great. There have been relatively few measurements of proteins and peptides, and most of the measurements were obtained by measuring the free amino acids before and after a hydrolysis step. Representative methods of this type have been described [245-259]. Since these methods are basically free amino acid methods, they will be discussed next in conjunction with those methods. 

The amino acid sequences of haptides comprise hydrophobic and cationic residues with a net charge of +4 to +5 per 19 to 21 amino acids. It was proposed that haptides could be attracted to the anionic liposomes as well as the anionic cell membrane and that the hydrophobic properties of the haptide facilitate membrane translocation (106). Haptide uptake was reported to be energy independent, occurring at 4°C. The advantage of this peptide compared to CPP such as TAT and Antp, is that, unlike the virus-derived peptides, the haptides are not recognized as foreign antigens and do not induce cell transformation (106). However, haptides have also been found to accelerate fibrin clot formation and lack cell specificity (106). 

The role of aspartic acid and glutamic acid was investigated in BMP (Beefy Meaty peptide, Lys-Gly-Asp-Glu-Glu-Ser-Leu-Ala) isolated from enzymatic digests of beef soup. The taste of BMP was affected by the sequence of acidic fragment. Sodium ion uptake of acidic dipeptides and their taste, when mixed with sodium ion, were dependent on the component and/or sequence of dipeptides containing acicHc amino acids. 

Lactic streptococci initiate casein degradation through the action of cell wall-associated and cell membrane-associated proteinases and peptidases. Small peptides are taken into the cell and hydrolyzed to their constituent amino acids by intracellular peptidases (Law and Sharpe 1978). Peptides containing four to seven residues can be transported into the cell by S. cremoris (Law et al. 1976B). S. lactis and S. cremoris have surface-bound peptidases and thus are not totally dependent on peptide uptake for protein use (Law 1979B). Some surface peptidases of S. cremoris are located in the cell membrane, whereas others are located at the cell wall-cell membrane interface (Exterkate 1984). Lactic streptococci have at least six different aminopeptidase activities, and can be divided into three groups based on their aminopeptidase profiles (Kaminogawa et al 1984). 

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