Purification and properties of a polymorphic high activity equine erythrocyte carbonic anhydrase.

A polymorphic form of the high activity or C-type of horse erythrocyte carbonic anhydrase has been isolated. It has been designated C2 and differs from the usual C1 form by having a cysteine replacement for arginine at residue 180. This second cysteine, unlike the other, is highly reactive. Isolation of the C2 isozyme by the usual methods results in most of it forming a mixed disulfide with glutathione and this product designated as C3 has an increased anodic mobility. The enzymatic activity and immunologic reactivity of both the C2 and C3 components are the same as for the usual C1 form of the enzyme. The C2 form can be stabilized by alkylation and the carboxamidomethyl derivative has been isolated in crystalline form.     

Thermophilic enrichment of microbial communities in the presence of the ionic liquid 1‐ethyl‐3‐methylimidazolium acetate

Aims

The aim of the study was to develop an approach to enrich ionic liquid tolerant micro‐organisms that efficiently decompose lignocellulose in a thermophilic and high‐solids environment.

Methods and Results

High‐solids incubations were conducted, using compost as an inoculum source, to enrich for thermophilic communities that decompose switchgrass in the presence of the ionic liquid 1‐ethyl‐3‐methylimidazolium acetate ([C2mim][OAc]). Ionic liquid levels were increased from 0 to 6% on a total weight basis incrementally. Successful enrichment of a community that decomposed lignocellulose at 55°C in the presence of 6% [C2mim][OAc] was achieved, when the [C2mim][OAc] level was increased stepwise from 2% to 4% to 5% to 6%. Pyrosequencing results revealed a shift in the community and a sharp decrease in richness, when thermophilic conditions were applied.

Conclusions

A community tolerant to a thermophilic, high‐solids environment containing 6% [C2mim][OAc] was enriched from compost. Gradually increasing [C2mim][OAc] concentrations allowed the community to adapt to [C2mim][OAc].

Significance and Impact of the Study

A successful approach to enrich communities that decompose lignocellulose under thermophilic high‐solids conditions in the presence of elevated levels of [C2mim][OAc] has been developed. Communities yielded from this approach will provide resources for the discovery of enzymes and metabolic pathways relevant to biomass pretreatment and fuel production.     

Sequence of the low activity equine erythrocyte carbonic anhydrase and delineation of the amino acid substitutions in various polymorphic forms

the sequence of the low activity form of equine erythrocyte carbonic anhydrase has been determined. The most common electrophoretic form, designated D, has been found to have five substitutions. Amino acid exchanges in the electrophoretic variants known as A1, A2, B, and T have been found at six other positions. The data do not permit calculation of the number of polymorphic forms of this enzyme. The equine D isozyme and the analogous human enzyme are quite homologous, 211 of their 260 residues, or 81%, being identical.     

The sequence of equine muscle carbonic anhydrase

The sequence of equine muscle carbonic anhydrase (CA-III) has been determined. The 2 reactive cysteines of the 5 such residues have been localized. A strong sequence homology to other mammalian carbonic anhydrases exists, and 91% of the residues in the equine and bovine muscle forms are identical.     

Some sulfhydryl properties and primary structure of human erythrocyte superoxide dismutase

Human Cu-Zn superoxide dismutase prepared by different methods shows varying properties relevant to its sulfhydryl chemistry. A cysteine residue not found in the analogous bovine enzyme appears to be responsible for its unusual lability. Alkylation of this cysteine results in a marked increase in stability, and this form of the protein may be readily crystallized. The primary structure of the 153 amino acid residues found in the human protein has been determined, and 82% of the residues are identical with those of the bovine enzyme. A significant variation is seen in the portion of those proteins comprising residues 17-36, with eleven changes being noted.     

Localization of lysines acetylated in ubiquitin reacted with p-nitrophenyl acetate

The protein ubiquitin undergoes extensive N epsilon-acetylation of some of its seven lysine residues when reacted with p-nitrophenyl acetate. Lysines 27 and 29 show little reactivity whereas residue 6 is the most readily acetylated. Residues 11, 33, 48, and 63 show intermediate reactivities.     

Isolation and crystallization of ubiquitin from mature erythrocytes

A relatively simple and reproducible procedure for the isolation of the active form of ubiquitin has been developed. The amount of this protein in mature erythrocytes appears to be about 0.15 mg. per gm. of hemoglobin and 60% of the material may be recovered. The protein can be crystallized from ammonium sulfate in the presence of mercaptan.     

Sequence of the high-activity equine erythrocyte carbonic anhydrase: N-terminal polymorphism (acetyl-ser/acetyl-thr) and homologies to similar mammalian isozymes

The amino acid sequence of the high-activity equine erythrocyte carbonic anhydrase (CA-II) has been determined. Two different N-termini are noted, the C₁ form having an N-acetyl-serine and the C₂ form an N-acetyl-threonine. The sequence of the equine enzyme is most homologous to the human CA-II isozyme, with 224 of the 259 residues being identical.This investigation was supported in part by United States Public Health Service Grant CA-1786 from the National Cancer Institute.