K.R. Lynn

Biochemical properties of latices from the Euphorbiaceae

Abstract Latex sera from 18 Euphorbia species were surveyed for protein, carbohydrate and total solid contents. Protease, esterase, alkaline and acid phosphatase, N -acetyl-β-glucosaminidase, α-mannosidase, α- and β-galactosidase, α- and β-glucosidase, α-amylase, lysozyme, leucine amino peptidase and cellulase activities were also measured. The effects of nine protease inhibitors were assayed as were haemagglutinating (lectin) contents. Two-dimensional (isoelectric focusing and SDS) PAGE maps of the sera were made. The results obtained show that the latices have widely varying biochemical properties.

Purification and characterization of hevain, a serine protease from Hevea brasiliensis

Abstract A serine protease of MW 69000 has been isolated, in homogeneous form, from the latex of Hevea brasiliensis . The enzyme, named hevain, has only limited esterolytic and proteolytic abilities, a maximum activity in the pH range 6.5–7.5, and a pI of 4.3. Hevain has a notably high content of acidic amino acids, while the aromatic residues are present in relatively minor amounts.

Proteases of Euphorbiaceae.

Abstract From lactices of eight species of the family Euphorbiaceae a total of 17 proteases have been isolated. The major characterstics of these enzymes are collected here for comparisons which demonstrate that the proteases are all serine-centred and carry essential histidine residues. They have, however, different physical properties such as Mrs, amino acid compositions and charged forms, and different reactivities to ester and protein substrates, and to protease inhibitors.

Euphorbain p, a serine protease from euphorbia pulcherrima

Abstract A serine protease named euphorbain p has been isolated in a homogeneous state from the latex of Euphorbia pulcherrima . This multi-chain enzyme, MW 74000, is similar in composition to one in E. lathyris , but is larger in size and has a more restricted activity. It has a pI of 4.7, and displays maximum activity at pH 7.0.

Hevains: Serine-centred proteases from the latex of Hevea brasiliensis

Abstract Hevains b and l , isolated respectively from the serum and lutoids of freeze-dried latex from Hevea brasiliensis , were purified to homogeneity and compared with hevain a from commercial, ammonia-treated latex. The M r s of hevains a and b are 69 000 and 58 000, respectively, and both exist in several charged forms. The amino acid compositions of the two enzymes differ significantly, but the reactivities to a variety of ester and protein substrates are similar, as are the pH optima. Hevain l is a distinct protease of M r 80 000 and unique amino acid composition. It displays esterolytic activity and will digest insulin B chain, but is not proteolytic to azocollagen, azocasein, bovine serum albumen or haemoglobin. The activities of all three enzymes are dependent on the presence of serine and histidine residues.

Three serine proteases from the latex of Euphorbia cyparissias

Abstract Three serine-centred proteolytic enzymes, euphorbains y-1, −2 and −3, were isolated from the latex of Euphorbia cyparissias . These proteases have different specific activities to azocoll and CBZ glycine p -nitrophenyl ester. The pIs and M r s of y-1, −2 and −3 are 5.2 and 67 000, 5.2 and 33 000, and 6.3 and 67 000, respectively. The enzymes, which are glycoproteins, are immunologically distinct from euphorbain 1, but clearly related to that enzyme in amino acid composition.

Two proteases from the latex of Elaeophorbia drupifera

Abstract Two serine-centred proteolytic enzymes containing catalytically essential histidine residues have been purified to homogeneity from the latex of Elaeophorbia drupifera . The high (117 K) M r , form, euphorbain d 1 , and the low M r , (65 K) form, euphorbain d 2 , are each composed of subunits of weight 30 000. The subunits differ slightly, as is seen by tryptic mapping and in the amino acid compositions reported for the proteases. Both enzymes have five isoelectric forms, and both display two pH maxima for proteolytic activity. Large molar excesses of sulphydryl-blocking reagents produce some activation of euphorbains d 1 and d 2 .

Lectins from latices of Euphorbia and Elaeophorbia species

Abstract Crude latex sera from 17 members of the genus Euphorbia and from Elaeophorbia drupifera (Euphorbiaceae) contained a wide range of agglutinating abilities. Homogeneous lectins were isolated from latices of Euphorbia coerulescens, E. hermentiana, E. lactea, E. lactea cristata, E. lathyris, E. trigona and Elaeophorbia drupifera . The M ,s of the lectins ranged from 60 to 67 000, and the unit weights from 27 to 38 000. pI measurements showed that each latex contained from five to 13 isolectins. The amino acid compositions of the seven lectins were determined: those from E. hermentiana, E. lactea, E. lactea cristata, E. trigona and Elaeophorbia drupifera are related.

Ficin E, a serine-centred protease from Ficus elastica

Abstract A protease of M , 50 000 was purified from the latex of Ficus elastica . The enzyme has a pI of 3.7 and pH optimum at 6.0. Its activity is dependent on serine and histidine residues. The amino acid composition is reported.

Four lysozymes from latex of Asclepias syriaca

Abstract Four lysozymes have been purified to homogeneity from the latex of Asclepias syriaca (milkweed). They have M r of about 28 000. The amino acid compositions of the four enzymes are different, but two are apparently related. The lysozymes have different sensitivities to the inhibitor histamine; all are relatively insensitive to N -acetyl- d -glucosamine and two have chitinase activity.