Print the first column

I want to print column 1 of this file. I used this command: awk '{print $1}' but it just printed the first word of the 1st column.

DATA

ABC transporters                             ABC transporters
Alanine, aspartate and glutamate metabolism  Alanine, aspartate 
alpha-Linolenic acid metabolism              alpha-Linolenic acid metabolism
Aminoacyl-tRNA biosynthesis                  Aminoacyl-tRNA biosynthesis
Amino sugar and nucleotide sugar metabolism  Amino sugar and nucleotide
Arachidonic acid metabolism                  Arachidonic 

Output:

ABC
Alanine,
alpha-Linolenic
Aminoacyl-tRNA
Amino
Arachidonic

Desired Output:

ABC transporters
Alanine, aspartate and glutamate metabolism
alpha-Linolenic acid metabolism 
Aminoacyl-tRNA biosynthesis 
Amino sugar and nucleotide sugar metabolism 
Arachidonic acid metabolism 

What I can see is that your columns are delimited by two space.

so with awk:

awk -F '\\s\\s' '{print $1}'

Since this seems to be a fixed-width column, you can just cut the corresponding characters. The widest column Alanine, aspartate and glutamate metabolism seems to be 44 characters wide, so:

$ cut -c1-44 foo
ABC transporters
Alanine, aspartate and glutamate metabolism
alpha-Linolenic acid metabolism
Aminoacyl-tRNA biosynthesis
Amino sugar and nucleotide sugar metabolism
Arachidonic acid metabolism

As the second column obviously repeats the beginning of the first column, I take this as criterion for the cut with sed, thus it does not depend on the column width:

sed 's/^\(.*\)\(.*\) \1$/\1\2/'

First pattern is the repeated part, backreferenced as \1 at the end of the line. You could add ;s/ *$// to remove the trailing spaces if they bother you.