Charles Alais

Étude comparée des caséino-glycopeptides formés par action de la présure sur les caséines de vache, de brebis et de chèvre: II. Étude de la partie non-peptidique

Abstract Comparative study of the caseino-glycopeptides obtained after rennin digestion of the caseins of the milk of cow, sheep and goat II. Study of the non-peptidic part The caseino-glycopeptides obtained after rennin digestion of different caseins contain a non-peptidic part, the amount of which varies according to the origin of the casein (cow, goat or sheep) and to its state of purity (entire casein, casein α or κ). This part contains phosphorus, galactose, galactosamine and sialic acid (N-acetylneuraminic acid and N-glycollylneuraminic acid) which is released by neuraminidase and occupies a terminal position. The caseino-glycopeptide of casein κ (cow) is distinguished by particular properties: (a) a high content of glucids (28.2%) especially of sialic acid (14.3%); (b) it is recovered for 100% by the sum of the amounts of peptides, glucids and bound phosphate; (c) it contains 74% of the glucids of the original casein; (d) the proportions of the three determined glucids are the same as in the original casein κ. The content of glucids in the other caseino-glycopeptides is not so high and they contain only 20–40% of the glucids of the original casein.

Amino acid composition of κ-casein and terminal amino acids of κ- and para-κ-casein☆

Abstract The amino acid composition of κ-casein is reported. Carboxypeptidase liberates Ser, Thr, Ala and Val from κ-casein, Leu and Phe from para-κ-casein. These Leu and Phe residues may be involved in the linkage (probably an ester linkage) split by rennin during its action on κ-casein.

Cow κ-casein: Structure of the carbohydrate portion☆

Abstract The detailed sugar sequences of the two main carbohydrate portions of cow κ-casein were established by enzymic and chemical methods and by mass spectrometry. The sugar sequences correspond to widespread sugar parts occurring in many glycoproteins.

The amino acid sequence of sheep κA-casein: II. Sequence studies concerning the κA-caseinoglycopeptide and establishment of the complete primary structure of the protein☆

The primary structure of sheep κA-caseinoglycopeptide, the C-terminal portion of fκA-casein released by chymosin, was established. The peptide was subjected to digestion with chymotrypsin and the chymotryptic peptides were purified by Sephadex G-50 filtration and Dowex 1X2 chromatography; their sequences were determined with a Sequencer. Alignment of the chymotryptic peptides into a chain containing 66 amino acids was possible by automated degradation of the caseinoglycopeptide up to the 45th amino acid. This study allowed the establishment of the complete sequence of sheep κA-casein (171 amino acids) which is indicated. For the first time a comparison between two κ-caseins (cow, sheep), substrates of chymosin (milk clotting process), was possible. Two deletions and 26 replacements, especially in the caseinoglycopeptide part, were noted, and the location of the carbohydrate part was indicated. Some structural features concerning the caseinoglycopeptides and the fibrinopeptides involved in the milk and blood clotting processes are briefly compared. Three examples of sequences of portions of cow or sheep κ-caseins and of human fibrinogen presenting homology are presented.

Étude de la Caséine κ de vache caractérisation de la liaison sensible à l'action de la présure

Abstract κ-Casein has been reduced by LiBH 4 . A precipitate (P) and a supernatant (S) containing a substance soluble in 12% trichloroacetic acid and not dialysable are obtained: they seem to be very closely related respectively to para-κ-casein and κ-caseino-glycopeptide both obtained after rennin-digestion of κ-casein. Phenylalanine is the C-terminal amino acid of para-κ-casein and phenylalaninol has been detected in the precipitate (P). LiBH 4 reduces the rennin-sensitive linkage in κ-casein which seems to be an ester linkage involving the carboxyl group of the C-terminal phenylalanine residue of para-κ-casein.

Comparative study of cow and sheep κ-caseinoglycopeptides: Determination of the N-terminal sequences with a sequencer and location of the sugars

the casein rniccile in its natural etivironment 111 and in-the clotting phenomenon induced by t&action of rennin (EC 3.4.4.3); it’ is also the only casein fraction hi cOIlti3iM sugars 12, 31, TO the hCtCXOgC&ty Of K-cascin from pooled milk are contributing the genetic variants, but also the non-identical composiPion of the carbohydrate groups present. This observation is in ~cordance with Cottschalk’s [4] concept on the hetcrogtineity of the eaibohydrate group iti glyeoprot&s_ During the rennin clotring of milk a. Phe-Met bond ,is split J5]. A large peptide, called K-macropepride wheri K-case+ is sugar-free or K-caseinoglycopeptide when K-casein is sugar-rich, is liberated and paraK-casein, .devoid of sugars, precipitates. Bovine K-caseino&copepticle has already been submitted to extensive structural studies [6-91 but only few data are available foi sheep K-caseinoglyc&peptide [5, IO, I1 ]_ The prcsqtt note iepcrts the deter&nation of the E-terminal sequence of the latter (48 amino acid residues) with a sequencer and some comparisons with cow Ec-chseinogllycopept?de; furthermore the locatic~~ of the short giycopeptide obtained indepe&entty Corn cow #-casehi by enzymic procedures is iliscvssed. Cow KA-casein was prepared according to McKenzie and Wake [ 12J from the milk of homozygous cows and sheep K-casein according to AIais and Jollih [ 1.3]_ The K-c%einoglycopeptides were obtained after rennin digestion of the corresponding K-caseins as previously described [ 141, Automated Edman degradation [ 151 was carried out in a E&man sequencer, Model

κ-Casein from bovine colostrum

90 E, by the quadrol method. The thiazolinones wer;: converted into PTH-amino acids and these latter were characterized by thin-layer chromatography, by gas-liquid chromatogiaphy (Beckman GC 45 chromatograph) or with an amino acid autoanalyzer after regeneration of the free amino acid_ Short glycopeptides were isolated from cow and sheep K=% casein= by enzymic digestions <neBeaminidase, EC 3_2_ I. 18; chymotrypsin, EC 3.4.4.5; pronase) and further purified by filtration on Sephadt-x C-25 and paper electrophoresis according to Fiat et al. [ 16]_ Their structures were established mainly by the manual Edman technique.

The chromatographic purification of human kappa-casein☆

Abstract Whole casein from colostrum contains more κ-casein than normal casein. Structural studies have shown that the caseinoglycopeptide (C-terminal moiety) of κ-casein seems to be already present at parturition. Colostrum κ-casein contains about two times more carbohydrate than normal casein and the presence of N-acetylglucosamine together with N-acetylgalactosamine suggests structural differences of its prosthetic group. The behaviour of the sugars after parturition is discussed.

Comparative study of two Mucor miehei acid proteinases. Purification and some molecular properties.

Abstract The fractionation of human casein was shown to be more difficult than that of caseins from ruminants. As human casein is digested by rennin, although less satisfactorily than with other caseins already studied, the purification of a κ-like reaction was attempted. Fractionations obtained by precipitation or chromatography gave rise to rennin-sensitive components. Two κ-like fractions could be characterized by chromatography on DEAE-cellulose in the presence of dissociating agents.

Comparative electrophoretical studies of human and rabbit caseins.

Abstract 1. 1. The aspartate proteinases from two strains of Mucor meihei (CBS 37065 and NRRL 3169) have been purified according to two procedures. 2. 2. Although molecular weight and NH 2 -terminus are identical the amino acid composition is rather different.