Zur Frage des pH-Optimums des Pepsins

Summary Natural and purified proteins were split by crystallized pepsin. The break down of substrates was followed by a turbidimetric method. pH optima were found from 1.5 to 3.8. Only unpurified egg albumin had two optima, crystallin had one in the acid range. Ovomucoid not being split by pepsin, the second peak at pH 3.79 is referred to conalbumin. While the disintegration of caseinogen becomes slow with decreasing acidity, this is not true for casein (paracasein) which is well split up to pH 3.28 (cows casein) or 3,73 (womens casein). Nevertheless, the optimum is in the range of 1.5–2.0, like most proteins. Above this limit, the following optima were found: fibrinogen 2.93, thrombin 2.78, edestin 3.08, crystallized hemoglobin 3.19, conalbumin 3.79.     

Gibt es peptisch-tryptische Abbaustufen des Gliadins mit Antigencharakter?

Summary Peptic and tryptic digestion of gluten and gliadin leaves a part of the substrates unaltered after precipitation at pH 4.5. Complement fixation test of the soluble part remains positive even after autoclaving of this part at pH 4.5, but not so after autoclaving at alkaline reaction. Positive reactions are also given by the components which are not ultrafiltrable while the ultrafiltrates give negative reactions. This means that positive reactions originate from residues of gluten or gliadin respectively. The question posed in the title must be answered in the negative. Products of peptic-tryptic digestion of gliadin do not have antigenic properties.     

A lipase in the milk of the gorilla

Zusammenfassung Gorillamilch hat nach Gallensäureaktivierung eine ähnlich spaltende Wirkung auf echte Fette wie Menschenmilch. Ohne Gallensäure kann hochmolekulares Fett auch im Zusammenwirken mit neutralisiertem menschlichem Magensaft oder Magenmucosaextrakten angegriffen werden, indem hierbei Di- und Monoglyzeride entstehen. Ebenso werden niedrig molekulare Ester direkt angegriffen wie zum Beispiel Tributyrin. Die Gorillamilch ist die einzige Tiermilch, bei der ein der Menschenmilch genau entsprechendes Verhalten der Lipase bisher gefunden wurde.

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Acknowledgment: The gorilla milk I obtained from Prof. K.Bernhard, Director of the Physiologisch-Chemisches Institut in Basel, who received it from Dr. E.Lang, Director of the Zoological Garden in Basel. I thank both gentlemen very much.     

Five amino acids in three HLA proteins explain most of the association between MHC and seropositive rheumatoid arthritis

The genetic association of the major histocompatibility complex (MHC) to rheumatoid arthritis risk has commonly been attributed to alleles in HLA-DRB1. However, debate persists about the identity of the causal variants in HLA-DRB1 and the presence of independent effects elsewhere in the MHC. Using existing genome-wide SNP data in 5,018 individuals with seropositive rheumatoid arthritis (cases) and 14,974 unaffected controls, we imputed and tested classical alleles and amino acid polymorphisms in HLA-A, HLA-B, HLA-C, HLA-DPA1, HLA-DPB1, HLA-DQA1, HLA-DQB1 and HLA-DRB1, as well as 3,117 SNPs across the MHC. Conditional and haplotype analyses identified that three amino acid positions (11, 71 and 74) in HLA-DRβ1 and single-amino-acid polymorphisms in HLA-B (at position 9) and HLA-DPβ1 (at position 9), which are all located in peptide-binding grooves, almost completely explain the MHC association to rheumatoid arthritis risk. This study shows how imputation of functional variation from large reference panels can help fine map association signals in the MHC.     

Catechine und Hydroxy-flavandiole als Gerbstoffbildner

Summary From the ranks of the colourless hydroxyflavans, four differenthydroxyflavan-3-ols(catechins and epi-catechins), as well as eight hydroxyflavan-3,4-diols, have so far been encountered in nature. These substances are also procurable by synthesis. On treatment with hot water or dilute acids, they are easily converted into soluble tannins or insoluble phlobaphenes. The mechanism of the self-condensation is explained using catechin via the isolation of a dimerie product. A probable path for the self-condensation of the diols has been indicated. In contrast to the products of their self-condensation, the monomeric polyhydroxyflavans are not real tannins. A particular accumulation of phenolhydroxyl groups in the molecule, the tendency to form supersaturated solutions and low solubility in water in the — generally not attainable — crystalline state are prerequisites for tanning properties. In nature, the self-condensation of polyhydroxyflavans proceeds (e. g. in the wood ofAcacia catechu or in Quebracho Wood) without the assistance of enzymes. Dehydrogenative polymerisation occurs with formation of brown or red phlobaphenes (e.g. in cocoa beam) which are generally insoluble.