Edwin B. Kalan

Isolubimin: A possible precursor of lubimin in infected potato slices

Abstract Potato slices treated with spirovetiva-1(10),11-diene-2-one yield lubimin and rishitin within 24 hr. A vetispirane which has not been detected in fungally infected potatoes was also isolated. This compound, isolubimin, appears to be an intermediate in the conversion of the above spirovetivone to lubimin.

The isolation and amino acid composition of two peptides from chymotryptic digests of β-lactoglobulins A and B

Abstract Short-term chymotryptic digests have been carried out with β-lactoglobulins A and B, performic acid-oxidized and S-sulfonated derivatives. Differences in the peptide patterns have been found after high-voltage electrophoresis only when disulfide bonds were previously cleaved. Two peptides have been isolated from chymotryptic digests of S-sulfonated β-lactoglobulins, and their amino acid compositions have been determined to be as follows: For the peptide from the β-A derivative: Asp 2 , Thr 1 , Glu 4 , Pro 1 , Ala 3 , Val 1 , Ileu 2 , Phe 1 , 1 2 Cys 1 , Lys 4 ; and for the peptide from β-B: Asp 1 , Thr 1 , Glu 4 , Pro 1 , Ala 3 , Val 1 , Ileu 2 , Phe 1 , 1 2 Cys 1 , Lys 4 , Gly 1 . The sole difference lies in the aspartic acid-glycine content. The valine-alanine difference in β-lactoglobulins A and B remains unaccounted for in the present study.

Ribonuclease B of bovine milk

Abstract Ribonuclease B has been isolated from 757 liters of milk; pilot plant facilities were used to provide a crude fraction. Final purification was achieved by gel filtration on Sephadex G-75 and chromatography on IRC-50. Milk ribonuclease A was also isolated by this procedure. Milk ribonuclease B has an amino acid composition which is identical to pancreatic ribonuclease A, milk ribonuclease A, and pancreatic ribonuclease B. It is a glycoprotein containing 4.2% hexosamine (3.0% glucosamine plus 1.2% galactosamine) and 5.17% mannose. It differs from pancreatic ribonuclease B, which contains 2.16% glucosamine, no galactosamine, and 5.7% mannose.

End-group analysis of αs1-caseins A, B, and C

Abstract Three genetically determined variants of αs1-casein have been prepared, and the purity of each has been verified by starch-gel-urea electrophoresis. The amino-terminal end group was determined qualitatively by two independent chemical methods. Arginine was the only amino-terminal amino acid revealed by each method for all three variants. The results of the action of carboxypeptidase A can be interpreted most simply to infer a leucyl-tryptophan carboxyl-terminal sequence for all three proteins. The kinetics of amino acid release by carboxypeptidase was similar for the three αs1-caseins. A molecular weight of ~31,000 was determined from the carboxypeptidase data, assuming a single polypeptide chain. The results indicate that all amino acid differences among the variants must occur within the polypeptide chain, if the latter assumption is valid.

Isoflavonoid changes in soybean cell suspensions when callenged with intact bacteria or fungal elicitors

Summary Glycine max (L.) Merr. cv. Mandarin cell suspension cultures did not give a typical hypersensitive response (HR) when challenged with a fungal elicitor or an incompatible strain of the soybean leaf pathogen Pseudomonas syringae cv. glycinea (Psg). Those cultures that darkened showed a small, gradual loss of viability and accumulated the phytoalexin glyceollin. Such cultures had a much higher level of isoflavonoids than those that did not darken or produced glyceollin under biotic stress. Concurrent with the formation of glyceollin, there was a sharp decline in the level of daidzein and genistein. Genistein was identified as a major isoflavonoid of soybean cell suspensions, but occurred only in trace amounts in the intact plant. No correlation was found between the induced levels of glyceollin and constitutive levels of isoflavonoids. While daidzein may be a direct precursor of glyceollin, a high level of daidzein and perhaps genistein appeared to be indicative of a required physiological state of the culture for the stress response. Cell culture levels of isoflavonoids appeared to be elevated by light.

Analysis of proteolytic digests of genetic variants of αs1-casein

Abstract The genetic variants, A, B, and C, of αs1-casein from cows milk were digested under controlled conditions with trypsin, chymotrypsin, and pepsin. The resulting peptides were examined by a mapping procedure and the patterns were compared within each set of digests. The B and C variants are known to differ in composition by a single amino acid substitution—a glutamic acid residue in B being replaced by a glycine in C. Probable difference peptides containing this substitution were observed in each set of proteolytic digestions. The results of specific staining for arginine, histidine, methionine, tyrosine, and tryptophan residues suggest that the presumed difference peptides are related and indicate the presence of several of these amino acids in the vicinity of the amino acid substitution. The αs1-casein A variant, which differs from the other two proteins quite substantially in amino acid composition, revealed peptide patterns almost identical to those of B and C, with the main difference being the absence of one or two major spots in A. The hypothesis is proposed that αs1-casein A, which represents an unusual type of genetic variant, is devoid of a portion of the molecule, with the remaining sequence similar to the B protein.

The action of phosphatases on casein fractions

Abstract Data have been presented to support the hypothesis that the phosphate linkages in α-, β-, and unfractionated casein are identical.

Reactivity of sulfhydryls in several β-lactoglobulins

Abstract Native cow β-lactoglobulins A and B, and goat and sheep β-lactoglobulins reacted with Ellmans reagent at identical rates, and all exhibited two sulfhydryl groups per mole (36,600 gm). Cow β-lactoglobulin C also contained two sulfhydryls per mole, but these reacted at only about one-tenth the rate of those in the other variants. The reactivity of the two sulfhydryl groups in a given variant appeared identical. Enzymic removal of the two carboxyl terminal residues of β-lactoglobulin B greatly increased the reactivity of the sulfhydryls to a rate comparable to that in the molecule denatured with sodium dodecyl sulfate. Denaturation, as measured by rate of reaction of sulfhydryls with Ellmans reagent, required a higher concentration of sodium dodecyl sulfate for β-lactoglobulin C than for β-lactoglobulin A, and least for β-lactoglobulin B.

Solanidine in potato (Solanum tuberosum) tuber tissue disrupted by Erwinia atroseptica and by Phytophthora infestans

Abstract Solanidine has been isolated and identified from potato tuber tissue disrupted by Erwinia atroseptica , and by Phytophthora infestans , in a compatible interaction. Tuber varieties, resistant to P. infestans in which cellular disintegration was not apparent, did not produce the aglycone. The evidence supports the view that solanidine is formed in disrupted tissue through the activity of hydrolytic potato enzymes on the glycoalkaloids.

The carboxyl terminal amino acids of β-lactoglobulins A and B

Abstract The release of amino acids from the carboxyl terminal end of β-lactoglobulins A and B has been studied with the use of carboxypeptidases A and B. The action of carboxypeptidase A catalyzes the hydrolysis of two moles of isoleucine and about one mole of histidine per mole of native protein at pH 8.5. The S-sulfo derivative releases two moles of isoleucine and two moles of histidine under the same conditions. When the native proteins were hydrolyzed with a combination of carboxypeptidases A and B, a wide spectrum of amino acids was found with leucine appearing as the amino acid following histidine. It appears that the two phenotypes, β-lactoglobulin A and β-lactoglobulin B, do not differ in the sequence of amino acids in the carboxyl-terminal portion of the molecules. In addition, they do not seem to differ in the manner they are hydrolyzed by the carboxypeptidase preparations.